3.11.0

Released on: Unreleased

Libraries

`dart:js_util`

dart2wasm no longer supports dart:js_util. Any code that imports dart:js_util will no longer compile with dart2wasm. Consequently, code that depends on package:js will no longer compile with dart2wasm either. The name dart.library.js_util is no longer a key in dart2wasm compilation environments, including in conditional imports and exports. See #61550 for more details.

3.10.0

Released on: Unreleased

Language

Dart 3.10 adds dot shorthands to the language. To use them, set your package's SDK constraint lower bound to 3.10 or greater (sdk: '^3.10.0').

Dart 3.10 also adjusts the inferred return type of a generator function (sync* or async*) to avoid introducing unneeded nullability.

Dot shorthands

Dot shorthands allow you to omit the type name when accessing a static member in a context where that type is expected.

These are some examples of ways you can use dot shorthands:

Color color = .blue;
switch (color) {
  case .blue:
    print('blue');
  case .red:
    print('red');
  case .green:
    print('green');
}

Column(
  crossAxisAlignment: .start,
  mainAxisSize: .min,
  children: widgets,
)

To learn more about the feature, check out the feature specification.

Eliminate spurious Null from generator return type

The following local function f used to have return type Iterable<int?>. The question mark in this type is spurious because the returned iterable will never contain null (return; stops the iteration, it does not add null to the iterable). This feature makes the return type Iterable<int>.

void main() {
  f() sync* {
    yield 1;
    return;
  }
}

This change may cause some code elements to be flagged as unnecessary. For example, f().first?.isEven is flagged, and f().first.isEven is recommended instead.

Tools

Analyzer

The analyzer includes a new plugin system. You can use this system to write your own analysis rules and IDE quick fixes.
- Analysis rules: Static analysis checks that report diagnostics (lints or warnings). You see these in your IDE and at the command line via dart analyze or flutter analyze.
- Quick fixes: Local refactorings that correct a reported lint or warning.
- Quick assists: Local refactorings available in the IDE that are not associated with a specific diagnostic.
See the documentation for writing an analyzer plugin, and the documentation for using analyzer plugins to learn more.
Lint rules which are incompatible with each other and which are specified in included analysis options files are now reported.
Offer to add required named field formal parameters in a constructor when a field is not initialized.
Support the new @Deprecated annotations by reporting warnings when specific functionality of an element is deprecated.
Offer to import a library for an appropriate extension member when method or property is accessed on a nullable value.
Offer to remove the const keyword for a constructor call which includes a method invocation.
Remove support for the deprecated @required annotation.
Add two assists to bind constructor parameters to an existing or a non-existing field.
Add a warning which is reported when an @experimental member is used outside of the package in which it is declared.
Add a new lint rule, remove_deprecations_in_breaking_versions, is added to encourage developers to remove any deprecated members when the containing package has a "breaking version" number, like x.0.0 or 0.y.0.
(Thanks @FMorschel for many of the above enhancements!)

Dart CLI and Dart VM

The Dart CLI and Dart VM have been split into two separate executables.

The Dart CLI tool has been split out of the VM into it's own embedder which runs in AOT mode. The pure Dart VM executable is called dartvm and has no Dart CLI functionality in it.

The Dart CLI executable parses the CLI commands and invokes the rest of the AOT tools in the same process, for the 'run' and 'test' commands it execs a process which runs dartvm.

dart hello.dart execs the dartvm process and runs the hello.dart file.

The Dart CLI is not generated for ia32 as we are not shipping a Dart SDK for ia32 anymore (support to execute the dartvm for ia32 architecture is retained).

Libraries

`dart:async`

Added Future.syncValue constructor for creating a future with a known value. Unlike Future.value, it does not allow an asynchronous Future<T> as the value of a new Future<T>.

`dart:core`

Breaking Change #61392: The Uri.parseIPv4Address function no longer incorrectly allows leading zeros. This also applies to Uri.parseIPv6Address for IPv4 addresses embedded in IPv6 addresses.
The Uri.parseIPv4Address adds start and end parameters to allow parsing a substring without creating a new string.
New annotations are offered for deprecating specific functionalities:
- @Deprecated.extend() indicates the ability to extend a class is deprecated.
- @Deprecated.implement() indicates the ability to implement a class or mixin is deprecated.
- @Deprecated.subclass() indicates the ability to extend a class or implement a class or mixin is deprecated.
- @Deprecated.mixin() indicates the ability to mix in a class is deprecated.
- @Deprecated.instantiate() indicates the ability to instantiate a class is deprecated.
The ability to implement the RegExp class and the RegExpMatch class is deprecated.

`dart:io`

Breaking Change #56468: Marked IOOverrides as an abstract base class so it can no longer be implemented.
Added ability to override behavior of exit(...) to IOOverrides.

`dart:js_interop`

JSArray.add is added to avoid cases where during migration from List to JSArray, JSAnyOperatorExtension.add is accidentally used. See #59830 for more details.
isA<JSBoxedDartObject> now checks that the value was the result of a toJSBox operation instead of returning true for all objects.
For object literals created from extension type factories, the @JS() annotation can now be used to change the name of keys in JavaScript. See #55138 for more details.
Compile-time checks for Function.toJS now apply to toJSCaptureThis as well. Specifically, the function should be a statically known type, cannot contain invalid types in its signature, cannot have any type parameters, and cannot have any named parameters.
On dart2wasm, typed lists that are wrappers around typed arrays now return the original typed array when unwrapped instead of instantiating a new typed array with the same buffer. This applies to both the .toJS conversions and jsify. See #61543 for more details.
Uint16ListToJSInt16Array is renamed to Uint16ListToJSUint16Array.
JSUint16ArrayToInt16List is renamed to JSUint16ArrayToUint16List.
The dart2wasm implementation of dartify now converts JavaScript Promises to Dart Futures rather than JSValues, consistent with dart2js and DDC. See #54573 for more details.
createJSInteropWrapper now additionally takes an optional parameter which specifies the JavaScript prototype of the created object, similar to createStaticInteropMock in dart:js_util. See #61567 for more details.

`dart:js_util`

dart2wasm no longer supports dart:js_util and will throw an UnsupportedError if any API from this library is invoked. This also applies to package:js/js_util.dart. package:js/js.dart continues to be supported. See #61550 for more details.

3.9.4

Released on: 2025-09-30

Pub

dart pub get --example will now resolve example/ folders in the entire workspace, not only in the root package. This fixes dart-lang/pub#4674 that made flutter pub get crash if the examples had not been resolved before resolving the workspace.

3.9.3

Released on: 2025-09-09

Tools

Development JavaScript compiler (DDC)

Fixes a pattern that could lead to exponentially slow compile times when static calls are deeply nested within a closure. When present this led to builds timing out or taking several minutes rather than several seconds.

3.9.2

Released on: 2025-08-27

Tools

Development JavaScript compiler (DDC)

Fixes an unintentional invocation of class static getters during a hot reload in a web development environment. This led to possible side effects being triggered early or crashes during the hot reload if the getter throws an exception.

3.9.1

Released on: 2025-08-20

This is a patch release that:

Fixes an issue in DevTools causing assertion errors in the terminal after clicking 'Clear' on the Network Screen (issue dart-lang/sdk#61187).
Fixes miscompilation to ARM32 when an app used a large amount of literals (issue flutter/flutter#172626).
Fixes an issue with git dependencies using tag_pattern, where the pubspec.lock file would not be stable when running dart pub get (issue dart-lang/pub#4644).

3.9.0

Released on: 2025-08-13

Language

Dart 3.9 assumes null safety when computing type promotion, reachability, and definite assignment. This makes these features produce more accurate results for modern Dart programs. As a result of this change, more dead_code warnings may be produced. To take advantage of these improvements, set your package's SDK constraint lower bound to 3.9 or greater (sdk: '^3.9.0').

Tools

Analyzer

The dart command-line tool commands that use the analysis server now run the AOT-compiled analysis server snapshot. These include dart analyze, dart fix, and dart language-server.

There is no functional difference when using the AOT-compiled analysis server snapshot. But various tests indicate that there is a significant speedup in the time to analyze a project.

In case of an incompatibility with the AOT-compiled snapshot, a --no-use-aot-snapshot flag may be passed to these commands. (Please file an issue with the appropriate project if you find that you need to use this flag! It will be removed in the future.) This flag directs the tool to revert to the old behavior, using the JIT-compiled analysis server snapshot. To direct the Dart Code plugin for VS Code to pass this flag, use the dart.analyzerAdditionalArgs setting. To direct the Dart IntelliJ plugin to pass this flag, use the dart.server.additional.arguments registry property, similar to these steps.
Add the switch_on_type lint rule.
Add the unnecessary_unawaited lint rule.
Support a new annotation, @awaitNotRequired, which is used by the discarded_futures and unawaited_futures lint rules.
Improve the avoid_types_as_parameter_names lint rule to include type parameters.
The definition of an "obvious type" is expanded for the relevant lint rules, to include the type of a parameter.
Many small improvements to the discarded_futures and unawaited_futures lint rules.
The code that calculates fixes and assists has numerous performance improvements.
A new "Remove async" assist is available.
A new "Convert to normal parameter" assist is available for field formal parameters.
New fixes are available for the following diagnostics:
- for_in_of_invalid_type
- implicit_this_reference_in_initializer
- prefer_foreach
- undefined_operator
- use_if_null_to_convert_nulls_to_bools
Numerous fixes and improvements are included in the "create method," "create getter," "create mixin," "add super constructor," and "replace final with var" fixes.
Dependencies listed in dependency_overrides in a pubspec.yaml file now have document links to pub.dev.
Improvements to type parameters and type arguments in the LSP type hierarchy.
Folding try/catch/finally blocks is now supported for LSP clients.
Improve code completion suggestions with regards to operators, extension members, named parameters, doc comments, patterns, collection if-elements and for-elements, and more.
Improve syntax highlighting of escape sequences in string literals.
Add "library cycle" information to the diagnostic pages.
(Thanks @FMorschel for many of the above enhancements!)

Dart build

Breaking change of feature in preview: dart build -f exe <target> is now dart build cli --target=<target>. See dart build cli --help for more info.

Dart Development Compiler (dartdevc)

Outstanding async code now checks and cancels itself after a hot restart if it was started in a different generation of the application before the restart. This includes outstanding Futures created by calling JSPromise.toDart from thedart:js_interop and the underlying the dart:js_util helper promiseToFuture. Dart callbacks will not be run, but callbacks on the JavaScript side will still be executed.
Fixed a soundness issue that allowed direct invocation of the value returned from a getter without any runtime checks when the getter's return type was a generic type argument instantiated as dynamic or Function.

A getter defined as:
```
class Container<T> {
  T get value => _value;
  ...
}
```
Could trigger the issue with a direct invocation:
```
Container<dynamic>().value('Invocation with missing runtime checks!');
```

Dart native compiler

Added cross-compilation support for target architectures of arm (ARM32) and riscv64 (RV64GC) when the target OS is Linux.

Pub

Git dependencies can now be version-solved based on git tags.

Use a tag_pattern in the descriptor and a version constraint, and all commits matching the pattern will be considered during resolution. For example:
```
dependencies:
  my_dependency:
    git:
      url: https://github.com/example/my_dependency
      tag_pattern: v{{version}}
    version: ^2.0.1
```
Starting from language version 3.9 the flutter constraint upper bound is now respected in your root package. For example:
```
name: my_app
environment:
  sdk: ^3.9.0
  flutter: 3.33.0
```
Results in dart pub get failing if invoked with a version of the Flutter SDK different from 3.33.0.

The upper bound of the flutter constraint is still ignored in packages used as dependencies. See flutter/flutter#95472 for details.

3.8.3

Released on: 2025-07-31

This is a patch release that:

Fixes an issue with the DevTools Network screen and Hot Restart (issue flutter/devtools#9203)
Fixes an issue when clearing the DevTools network screen (issue #61187)

3.8.2

Released on: 2025-07-16

This is a patch release that:

Fixes an issue with the size of cross-compiled binaries (issue #61097)

3.8.1

Released on: 2025-05-28

This is a patch release that:

Fixes an issue in DDC with late variables being incorrectly captured within async function bodies (issue #60748).

3.8.0

Released on: 2025-05-20

Language

Dart 3.8 adds null-aware elements to the language. To use them, set your package's SDK constraint lower bound to 3.8 or greater (sdk: '^3.8.0').

Null-aware elements

Null-aware elements make it easier to omit a value from a collection literal if it's null. The syntax works in list literals, set literals, and map literals. Within map literals, both null-aware keys and values are supported. Here is an example a list literal written in both styles, without using null-aware elements and using them:

String? lunch = isTuesday ? 'tacos!' : null;

var withoutNullAwareElements = [
  if (lunch != null) lunch,
  if (lunch.length != null) lunch.length!,
  if (lunch.length case var length?) length,
];

var withNullAwareElements = [
  ?lunch,
  ?lunch.length,
  ?lunch.length,
];

To learn more about null-aware collection elements, check out the documentation and the feature specification.

Libraries

`dart:core`

Added Iterable.withIterator constructor.

`dart:io`

Added HttpClientBearerCredentials.
Updated Stdout.supportsAnsiEscapes and Stdin.supportsAnsiEscapes to return true for TERM containing tmux values.

`dart:html`

Breaking change: Native classes in dart:html, like HtmlElement, can no longer be extended. Long ago, to support custom elements, element classes exposed a .created constructor that adhered to the v0.5 spec of web components. On this release, those constructors have been removed and with that change, the classes can no longer be extended. In a future change, they may be marked as interface classes as well. This is a follow up from an earlier breaking change in 3.0.0 that removed the registerElement APIs. See #53264 for details.

`dart:ffi`

Added Array.elements which exposes an Iterable over the Array's content.

Tools

Analyzer

The analyzer now supports "doc imports," a new comment-based syntax which enables external elements to be referenced in documentation comments without actually importing them. See the documentation for details.
Code completion is improved to offer more valid suggestions. In particular, the suggestions are improved when completing text in a comment reference on a documentation comment for an extension, a typedef, or a directive (an import, an export, or a library). Additionally, instance members can now be suggested in a documentation comment reference.
Offer additional assist to wrap a Flutter widget with a FutureBuilder widget.
Add a quick assist to wrap with ValueListenableBuilder.
Add a quick fix to convert an (illegal) extension field declaration into a getter declaration.
Add a quick fix to help code comply with a few lint rules that encourage omitting types: omit_local_variable_types, omit_obvious_local_variable_types, and omit_obvious_property_types.
Add a quick fix to create an extension method to resolve an "undefined method invocation" error.
Renaming a closure parameter is now possible.
Renaming a field now adjusts implicit this references in order to avoid name collisions.
Renaming a field formal parameter now properly renames known super-parameters in subclasses in other libraries.
Renaming a method parameter now properly renames across the type hierarchy.
The "encapsulate field" quick assist now works on final fields.
The "inline method" refactoring now properly handles inner closures.
The quick fix that adds names to a show clause or removes names from a hide clause can now add or remove multiple names simultaneously, in order to resolve as many "undefined" errors as possible.
The "remove const" quick fix now operates on more types of code.
The "add missing required argument" quick fix can now add multiple missing required arguments.
Add a new warning that reports an import or export directive with multiple show or hide clauses, which are never necessary.
Add a quick fix for this warning.
Add LSP document links for lint rules in analysis options files.
Add LSP document links for dependency packages in pubspec files.
Fix various issues around patterns, like highlighting, navigation, and autocompletion.
Add the use_null_aware_elements lint rule.
Add the experimental unnecessary_ignore lint rule.
(Thanks @FMorschel for many of the above enhancements!)

Dart Development Compiler (dartdevc)

In order to align with dart2js semantics, DDC will now throw a runtime error when a redirecting factory is torn off and one of its optional non-nullable parameters is provided no value. The implicit null passed to the factory will not match the non-nullable type and this will now throw.

In the future this will likely be a compile-time error and will be entirely disallowed.

Dart to Javascript Compiler (dart2js)

Removed the --experiment-new-rti and --use-old-rti flags.

Dart native compiler

Added cross-compilation support for the Linux x64 and Linux ARM64 target platforms.

Dart format

In 3.7.0, we released a largely rewritten formatter supporting a new "tall" style. Since then, we've gotten a lot of feedback and bug reports and made a number of fixes in response to that.

Features

Some users strongly prefer the old behavior where a trailing comma will be preserved by the formatter and force the surrounding construct to split. That behavior is supported again (but off by default) and can enabled by adding this to a surrounding analysis_options.yaml file:

formatter:
  trailing_commas: preserve

This is similar to how trailing commas work in the old short style formatter applied to code before language version 3.7.

Bug fixes

Don't add a trailing comma in lists that don't allow it, even when there is a trailing comment (issue dart-lang/dart_style#1639).

Style changes

The following style changes are language versioned and only affect code whose language version is 3.8 or later. Dart code at 3.7 or earlier is formatted the same as it was before.

Allow more code on the same line as a named argument or =>.

// Before:
function(
  name:
      (param) => another(
        argument1,
        argument2,
      ),
);

// After:
function(
  name: (param) => another(
    argument1,
    argument3,
  ),
);

Allow the target or property chain part of a split method chain on the RHS of =, :, and =>.

// Before:
variable =
    target.property
        .method()
        .another();

// After:
variable = target.property
    .method()
    .another();

Allow the condition part of a split conditional expression on the RHS of =, :, and =>.

// Before:
variable =
    condition
    ? longThenBranch
    : longElseBranch;

// After:
variable = condition
    ? longThenBranch
    : longElseBranch;

Don't indent conditional branches redundantly after =, :, and =>.

// Before:
function(
  argument:
      condition
          ? thenBranch
          : elseBranch,
)

// After:
function(
  argument:
      condition
      ? thenBranch
      : elseBranch,
)

Indent conditional branches past the operators.

// Before:
condition
    ? thenBranch +
        anotherOperand
    : elseBranch(
      argument,
    );

// After:
condition
    ? thenBranch +
          anotherOperand
    : elseBranch(
        argument,
      );

Block format record types in typedefs:

// Before:
typedef ExampleRecordTypedef =
    (
      String firstParameter,
      int secondParameter,
      String thirdParameter,
      String fourthParameter,
    );

// After:
typedef ExampleRecordTypedef = (
  String firstParameter,
  int secondParameter,
  String thirdParameter,
  String fourthParameter,
);

Eagerly split argument lists whose contents are complex enough to be easier to read spread across multiple lines even if they would otherwise fit on a single line.

The heuristic is that the argument list must contain at least three named arguments, some of which are nested and some of which are not.
```
// Before:
TabBar(tabs: [Tab(text: 'A'), Tab(text: 'B')], labelColor: Colors.white70);

// After:
TabBar(
  tabs: [
    Tab(text: 'A'),
    Tab(text: 'B'),
  ],
  labelColor: Colors.white70,
);
```

3.7.3

Released on: 2025-04-16

This is a patch release that:

Fixes a performance regression in the analysis server (issue #60335).

3.7.2

Released on: 2025-03-12

This is a patch release that:

Fixes a bug in dart2wasm that imports a js-string builtin function with a non-nullable parameter type where it must use a nullable one (issue #59899).

3.7.1

Released on: 2025-02-26

This is a patch release that:

Fixes a bug in the DevTools network profiler that was causing network traffic to be dropped (issue #8888).
Fixes a bug in DDC that prevents code from compiling when it includes factory constructors containing generic local functions (issue #160338).
Fixes a bug in the CFE that didn't correctly mark wildcard variables in formal parameters, causing the wildcard variables to appear in variable lists while debugging (issue #60121).

3.7.0

Released on: 2025-02-12

Language

Dart 3.7 adds wildcard variables and inference using bounds to the language. To use them, set your package's SDK constraint lower bound to 3.7 or greater (sdk: '^3.7.0').

Wildcard variables

Local variables and parameters named _ are now non-binding and they can be declared multiple times without collisions. You will no longer be able to use these variables nor access their values. All wildcard variable declaration types that have this behavior are described in the wildcard variables specification.

Top-level variables, top-level function names, type names, member names, etc. are unchanged. They can be named _ and used as they are today.

These are a few examples of where wildcard variables can be used:

Foo(_, this._, super._, void _()) {}

void main() {
  var _ = 1;
  int _ = 2;

  list.where((_) => true);
}

Inference using bounds

With the inference using bounds feature, Dart's type inference algorithm generates constraints by combining existing constraints with the declared type bounds, not just best-effort approximations.

This is especially important for F-bounded types, where inference using bounds correctly infers that, in the example below, X can be bound to B. Without the feature, the type argument must be specified explicitly: f<B>(C()):

class A<X extends A<X>> {}

class B extends A<B> {}

class C extends B {}

void f<X extends A<X>>(X x) {}

void main() {
  f(B()); // OK.

  // OK with this feature. Without it, inference fails after detecting
  // that C is not a subtype of A<C>.
  f(C());

  f<B>(C()); // OK.
}

The feature is described in more details in the inference using bounds specification.

Other language changes

Breaking Change #56893: If a field is promoted to the type Null using is or as, this type promotion is now properly accounted for in reachability analysis. This makes the type system more self-consistent, because it mirrors the behavior of promoted local variables. This change is not expected to make any difference in practice.

Tools

Analyzer

Add a new 'Go to imports' command to find the import directives that export a declaration.
Assists and quick fixes that add an import now consider the prefer_relative_imports and always_use_package_imports lint rules.
Add a new fix that converts a ~/ operation into /, when the ~/ operation is not available.
Add a fix that wraps an expression in await if the expression is currently not assignable, but awaiting it would make it assignable.
Assists and quick fixes that convert a forEach call into a for-loop now consider the prefer_final_in_for_each and always_specify_types lint rules.
Add an additional fix to correct a cascade_invocations lint rule violation.
Offer additional assists to wrap a Flutter widget with an Expanded widget, and with a Flexible widget.
Offer an assist to "inline" an else-block's inner if-statement with the else-block to read else if.
Add a fix to use_decorated_box by swapping the Container with ColoredBox as suggested by the lint.
Add an additional fix to import an unknown prefixed identifier by updating the show combinator on an existing import.
Add a fix to import an unknown prefixed identifier by adding an import directive with the given prefix.
Add a fix to import an unknown prefixed identifier by removing a hide combinator.
Add a fix to import an unknown identifier by adding an import directive with a show combinator, and optionally a prefix.
Code completion now suggests instance variables when completing inside the initializer of a late field.
Assists and quick fixes that add a const keyword now consider the prefer_const_declarations lint rule, preferring to add const to a variable declaration rather than the initial value.
Add a fix to add a missing on keyword in an extension declaration.
Add a fix to wrap an ambiguous property access or method call in an extension override. (Thanks @FMorschel for the above enhancements!
The 'sort members' command now considers the sort_constructors_first lint rule.
The 'extract method' refactoring now uses generic method syntax for function-typed parameters.
Add quick fixes for more than 30 diagnostics.
Add the strict_top_level_inference lint rule.
Add the unnecessary_underscores lint rule.
Add the experimental specify_nonobvious_property_types lint rule.
Add the experimental omit_obvious_property_types lint rule.
Add the experimental unnecessary_async lint rule.
Add the experimental unsafe_variance lint rule.
Remove the package_api_docs lint rule.
Remove the unsafe_html lint rule.

Dart format

The formatter implements a new style better suited for the kind of declarative code that many Dart users are writing today. The new style looks similar to the style you get when you add trailing commas to argument lists, except that now the formatter will add and remove those commas for you.

The dart format command uses the language version of each input file to determine which style it gets. If the language version is 3.6 or lower, the code is formatted with the old style. If 3.7 or later, it gets the new tall style.

You typically control the language version by setting a min SDK constraint in your package's pubspec. This means that when you update the SDK constraint in your pubspec to move to 3.7, you are also opting in to the new style.

In order to correctly determine the language version of each file it formats, dart format (like other dart commands) looks for a package_config.json file surrounding the files being formatted. This means that you need to run dart pub get before formatting code in your package. If you have format checks in your continuous integration server, you'll want to make sure it runs dart pub get too.

We don't intend to support both styles indefinitely. At some point in the future when most of the ecosystem is on 3.7 or later, support for the old style will be removed.

In addition to the new formatting style, a number of other changes are included, some of them breaking:

Project-wide page width configuration. By long request, you can now configure your preferred formatting page width on a project-wide basis. When formatting a file, the formatter will look in the file's directory and any surrounding directories for an analysis_options.yaml file. If it finds one, it looks for YAML like so:
```
formatter:
  page_width: 123
```
If it finds a page width matching that schema, then the file is formatted using that width. Since the formatter will walk the surrounding directories until it finds an analysis_options.yaml file, this can be used to globally set the page width for an entire directory, package, or even collection of packages. Since analysis_options.yaml files already support an include key to reference other analysis_options.yaml files, you can define a single configuration and share it across a number of packages.
Opting out a region of code from formatting. In code formatted using the new style, you can use a pair of special marker comments to opt a region of code out of automated formatting:
```
main() {
  this.isFormatted();
  // dart format off
  no   +   formatting
    +
      here;
  // dart format on
  formatting.isBackOnHere();
}
```
The comments must be exactly // dart format off and // dart format on. A file may have multiple regions, but they can't overlap or nest.

This can be useful for highly structured data where custom layout helps the reader understand the data, like large lists of numbers.
Overriding the page width for a single file. In code formatted using the new tall style, you can use a special marker comment to control the page width that it's formatted using:
```
// dart format width=30
main() {
  someExpression +
      thatSplitsAt30;
}
```
This comment must appear before any code in the file and must match that format exactly. The width set by the comment overrides the width set by any surrounding analysis_options.yaml file.

This feature is mainly for code generators that generate and immediately format code but don't know about any surrounding analysis_options.yaml that might be configuring the page width. By inserting this comment in the generated code before formatting, it ensures that the code generator's behavior matches the behavior of dart format.

End users should mostly use analysis_options.yaml for configuring their preferred page width (or do nothing and continue to use the default page width of 80).
Breaking change: Remove support for dart format --fix. Instead, use dart fix. It supports all of the fixes that dart format --fix could apply and many more.
Treat the --stdin-name name as a path when inferring language version. When reading input on stdin, the formatter still needs to know its language version to know what style to apply. If the --stdin-name option is set, then that is treated as a file path and the formatter looks for a package config surrounding that file path to infer the language version from.

If you don't want that behavior, pass in an explicit language version using --language-version=, or use --language-version=latest to parse the input using the latest language version supported by the formatter.

If --stdin-name and --language-version are both omitted, then the formatter parses stdin using the latest supported language version.
Rename the --line-length option to --page-width. This is consistent with the public API, internal implementation, and docs, which all use "page width" to refer to the limit that the formatter tries to fit code into.

The --line-length name is still supported for backwards compatibility, but may be removed at some point in the future. You're encouraged to move to --page-width. Use of this option (however it's named) is rare, and will likely be even rarer now that project-wide configuration is supported, so this shouldn't affect many users.

Dart to Javascript Compiler (dart2js)

The dart2js compiler which is invoked when the command dart compile js is used has been switched to use an AOT snapshot instead of a JIT snapshot.

Dart Development Compiler (dartdevc)

The dartdevc compiler and kernel_worker utility have been switched to use an AOT snapshot instead of a JIT snapshot, the SDK build still includes a JIT snapshot of these tools as package:build and package:build_web_compiler depend on it. The AOT snapshot can be used as follows to run DDC:

<dart-sdk>/bin/dartaotruntime <dart-sdk>/bin/snapshots/dartdevc_aot.dart.snapshot <options>

Libraries

`dart:html`

dart:html is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop and package:web. See #59716.

`dart:indexed_db`

dart:indexed_db is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop and package:web. See #59716.

`dart:io`

HttpException will be thrown by HttpClient and HttpServer if a NUL (0x00) appears in a received HTTP header value.

`dart:svg`

dart:svg is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop and package:web. See #59716.

`dart:web_audio`

dart:web_audio is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop and package:web. See #59716.

`dart:web_gl`

dart:web_gl is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop and package:web. See #59716.

`dart:js`

dart:js is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop. See #59716.

`dart:js_util`

dart:js_util is marked deprecated and will be removed in an upcoming release. Users should migrate to using dart:js_interop. See #59716.

3.6.2

Released on: 2025-01-30

Fixes a bug where HttpServer responses were not correctly encoded if a "Content-Type" header was set (issue #59719).
Fix dart format to parse code at language version 3.6 so that digit separators can be parsed correctly (issue #59815, dart_style issue #1630).
Fixes an issue where the DevTools analytics did not distinguish between new and legacy inspector events (issue #59884).
When running dart fix on a folder that contains a library with multiple files and more than one needs a fix, the fix will now be applied correctly only once to each file (issue #59572).

3.6.1

Released on: 2025-01-08

When inside a pub workspace, pub get will now delete stray .dart_tool/package_config.json files in directories between the workspace root and workspace directories. Preventing confusing behavior when migrating a repository to pub workspaces (issue pub#4445).
Fixes crash during AOT and dart2wasm compilation which was caused by the incorrect generic covariant field in a constant object (issue #57084).
Fixes analysis options discovery in the presence of workspaces (issue #56552).

3.6.0

Released on: 2024-12-11

Language

Dart 3.6 adds digit separators to the language. To use them, set your package's SDK constraint lower bound to 3.6 or greater (sdk: '^3.6.0').

Digit separators

Digits in number literals (decimal integer literals, double literals, scientific notation literals, and hexadecimal literals) can now include underscores between digits, as "digit separators." The separators do not change the value of a literal, but can serve to make the number more readable.

100__000_000__000_000__000_000  // one hundred million million millions!
0x4000_0000_0000_0000
0.000_000_000_01
0x00_14_22_01_23_45  // MAC address

Separators are not allowed at the start of a number (this would be parsed as an identifier), at the end of a number, or adjacent to another character in a number, like ., x, or the e in scientific notation.

Breaking Change #56065: The context used by the compiler and analyzer to perform type inference on the operand of a throw expression has been changed from the "unknown type" to Object. This makes the type system more self-consistent, because it reflects the fact that it's not legal to throw null. This change is not expected to make any difference in practice.

Libraries

`dart:io`

Breaking Change #52444: Removed the Platform() constructor, which has been deprecated since Dart 3.1.
Breaking Change #53618: HttpClient now responds to a redirect that is missing a "Location" header by throwing RedirectException, instead of StateError.

`dart:js_interop`

Added constructors for JSArrayBuffer, JSDataView, and concrete typed array types e.g. JSInt8Array.
Added length and []/[]= operators to JSArray.
Added toJSCaptureThis so this is passed in from JavaScript to the callback as the first parameter.
Added a static from method on JSArray to create a JSArray from a given JavaScript iterable or array-like object.

Tools

CFE

Breaking Change #56466: The implementation of the UP and DOWN algorithms in the CFE are changed to match the specification and the corresponding implementations in the Analyzer. The upper and lower closures of type schemas are now computed just before they are passed into the subtype testing procedure instead of at the very beginning of the UP and DOWN algorithms.

Dart format

Preserve type parameters on old-style function-typed formals that also use this. or super..
Correctly format imports with both as and if clauses.

Wasm compiler (dart2wasm)

The condition dart.library.js is now false on conditional imports in dart2wasm. Note that it was already a static error to import dart:js directly (see #55266).

Pub

Support for workspaces. This allows you to develop and resolve multiple packages from the same repo together. See https://dart.dev/go/pub-workspaces for more info.
New command dart pub bump. Increments the version number of the current package.

For example: dart pub bump minor will change the version from 1.2.3 to 1.3.0.
New validation: dart pub publish will warn if your git status is not clean.
New flag dart pub upgrade --unlock-transitive.
dart pub upgrade --unlock-transitive pkg, will unlock and upgrade all the dependencies of pkg instead of just pkg.

Analyzer

Add the use_truncating_division lint rule.
Add the experimental omit_obvious_local_variable_types lint rule.
Add the experimental specify_nonobvious_local_variable_types lint rule.
Add the experimental avoid_futureor_void lint rule.
Add quick fixes for more than 14 diagnostics.
Add new assists: "add digit separators", "remove digit separators", and "invert conditional expression".

3.5.3 - 2024-09-11

Fixes an issue with the DevTools Memory tool causing OOMs. and an issue resulting in a missing tab bar when DevTools is embedded in IntelliJ and Android Studio (issue#56607).
Fixes an issue with the DevTools release notes showing each time DevTools is opened instead of only the first time (issue#56607).
Fixes an issue resulting in a missing tab bar when DevTools is embedded in IntelliJ and Android Studio (issue#56607).

3.5.2 - 2024-08-28

Fixes a bug where ZLibDecoder would incorrectly attempt to decompress data past the end of the zlib footer (issue #56481).
Fixes issue where running dart from PATH could result in some commands not working as expected (issues #56080, #56306, #56499).
Fixes analysis server plugins not receiving setContextRoots requests or being provided incorrect context roots in multi-package workspaces (issue #56475).

3.5.1 - 2024-08-14

Fixes resolving include: in analysis_options.yaml file in a nested folder in the workspace (issue#56464).
Fixes source maps generated by dart compile wasm when optimizations are enabled (issue #56423).
Fixes a bug in the dart2wasm compiler in unsound -O3 / -O4 modes where a implicit setter for a field of generic type will store null instead of the field value (issue #56374).
Fixes a bug in the dart2wasm compiler that can trigger in certain situations when using partial instantiations of generic tear-offs (constructors or static methods) in constant expressions (issue #56440).
The algorithm for computing the standard upper bound of two types, also known is UP, is provided the missing implementation for StructuralParameterType objects. In some corner cases cases the lacking implementation resulted in a crash of the compiler (issue #56457).

3.5.0 - 2024-08-06

Language

Breaking Change #55418: The context used by the compiler to perform type inference on the operand of an await expression has been changed to match the behavior of the analyzer. This change is not expected to make any difference in practice.
Breaking Change #55436: The context used by the compiler to perform type inference on the right hand side of an "if-null" expression (e1 ?? e2) has been changed to match the behavior of the analyzer. change is expected to have low impact on real-world code. But in principle it could cause compile-time errors or changes in runtime behavior by changing inferred types. The old behavior can be restored by supplying explicit types.

Libraries

`dart:core`

Breaking Change #44876: DateTime on the web platform now stores microseconds. The web implementation is now practically compatible with the native implementation, where it is possible to round-trip a timestamp in microseconds through a DateTime value without rounding the lower digits. This change might be breaking for apps that rely in some way on the .microsecond component always being zero, for example, expecting only three fractional second digits in the toString() representation. Small discrepancies in arithmetic due to rounding of web integers may still occur for extreme values, (1) microsecondsSinceEpoch outside the safe range, corresponding to dates with a year outside of 1685..2255, and (2) arithmetic (add, subtract, difference) where the Duration argument or result exceeds 570 years.

`dart:io`

Breaking Change #55786: SecurityContext is now final. This means that SecurityContext can no longer be subclassed. SecurityContext subclasses were never able to interoperate with other parts of dart:io.
A ConnectionTask can now be created using an existing Future<Socket>. Fixes #55562.

`dart:typed_data`

Breaking Change #53785: The unmodifiable view classes for typed data have been removed. These classes were deprecated in Dart 3.4.

To create an unmodifiable view of a typed-data object, use the asUnmodifiableView() methods added in Dart 3.3.
Added superinterface TypedDataList to typed data lists, implementing both List and TypedData. Allows abstracting over all such lists without losing access to either the List or the TypedData members. A ByteData is still only a TypedData, not a list.

`dart:js_interop`

Breaking Change #55508: importModule now accepts a JSAny instead of a String to support other JS values as well, like TrustedScriptURLs.
Breaking Change #55267: isTruthy and not now return JSBoolean instead of bool to be consistent with the other operators.
Breaking Change ExternalDartReference no longer implements Object. ExternalDartReference now accepts a type parameter T with a bound of Object? to capture the type of the Dart object that is externalized. ExternalDartReferenceToObject.toDartObject now returns a T. ExternalDartReferenceToObject and ObjectToExternalDartReference are now extensions on T and ExternalDartReference<T>, respectively, where T extends Object?. See #55342 and #55536 for more details.
Fixed some consistency issues with Function.toJS across all compilers. Specifically, calling Function.toJS on the same function gives you a new JS function (see issue #55515), the maximum number of arguments that are passed to the JS function is determined by the static type of the Dart function, and extra arguments are dropped when passed to the JS function in all compilers (see #48186).

Tools

Analyzer

Add the unintended_html_in_doc_comment lint rule.
Add the invalid_runtime_check_with_js_interop_types lint rule.
Add the document_ignores lint rule.
Add quick fixes for more than 70 diagnostics.
The "Add missing switch cases" quick fix now adds multiple cases, such that the switch becomes exhaustive.
The "Remove const" quick fix now adds const keywords to child nodes, where appropriate.

Pub

New flag dart pub downgrade --tighten to restrict lower bounds of dependencies' constraints to the minimum that can be resolved.

Dart Runtime

The Dart VM only executes sound null safe code, running of unsound null safe code using the option --no-sound-null-safety has been removed.
Dart_NewListOf and Dart_IsLegacyType functions are removed from Dart C API.
Dart_DefaultCanonicalizeUrl is removed from the Dart C API.

3.4.4 - 2024-06-12

This is a patch release that:

Fixes an issue where pub would crash when failing to fetch advisories from the server. (issue pub#4269).
Fixes an issue where const bool.fromEnvironment('dart.library.ffi') is true and conditional import condition dart.library.ffi is true in dart2wasm. (issue #55948).
Fixes an issue where FFI calls with variadic arguments on MacOS Arm64 would mangle the arguments. (issue #55943).

3.4.3 - 2024-06-05

This is a patch release that:

Fixes an issue where DART_VM_OPTIONS were not correctly parsed for standalone Dart executables created with dart compile exe (issue #55818).
Fixes a bug in dart2wasm that can result in a runtime error that says array.new_fixed() has a constant larger than 10000 (issue #55873).
Adds support for --enable-experiment flag to dart compile wasm (issue #55894).
Fixes an issue in dart2wasm compiler that can result in incorrect nullability of type parameter (see #55895).
Disallows dart:ffi imports in user code in dart2wasm (e.g. issue [#53910]) as dart2wasm's currently only supports a small subset of dart:ffi (issue #55890).

3.4.2 - 2024-05-29

This is a patch release that:

Marks dart compile wasm as no longer experimental.
Fixes two bugs in exception handling in async functions in dart2wasm (issues #55347, #55457).
Fixes restoration of this variable in sync* and async functions in dart2wasm.
Implements missing control flow constructs (exceptions, switch/case with yields) in sync* in dart2wasm (issues #51342, #51343).
Fixes a bug dart2wasm compiler that surfaces as a compiler crash when indexing lists where the compiler proofs the list to be constant and the index is out-of-bounds (issue #55817).

3.4.1 - 2024-05-22

This is a patch release that:

Fixes a bug in the CFE which could manifest as compilation errors of Flutter web apps when compiled with dart2wasm (issue #55714).
Fixes a bug in the pub client, such that dart run will not interfere with Flutter l10n (at least for most cases) (issue #55758).

3.4.0 - 2024-05-14

Language

Dart 3.4 makes improvements to the type analysis of conditional expressions (e1 ? e2 : e3), if-null expressions (e1 ?? e2), if-null assignments (e1 ??= e2), and switch expressions (switch (e) { p1 => e1, ... }). To take advantage of these improvements, set your package's SDK constraint lower bound to 3.4 or greater (sdk: '^3.4.0').

Breaking Change #54640: The pattern context type schema for cast patterns has been changed from Object? to _ (the unknown type), to align with the specification. This change is not expected to make any difference in practice.
Breaking Change #54828: The type schema used by the compiler front end to perform type inference on the operand of a null-aware spread operator (...?) in map and set literals has been made nullable, to match what currently happens in list literals. This makes the compiler front end behavior consistent with that of the analyzer. This change is expected to be very low impact.

Libraries

`dart:async`

Added option for ParallelWaitError to get some meta-information that it can expose in its toString, and the Iterable<Future>.wait and (Future,...,Future).wait extension methods now provide that information. Should make a ParallelWaitError easier to log.

`dart:cli`

Breaking change #52121: waitFor is removed in 3.4.

`dart:ffi`

Added Struct.create and Union.create to create struct and union views of the sequence of bytes stored in a subtype of TypedData.

`dart:io`

Breaking change #53863: Stdout has a new field lineTerminator, which allows developers to control the line ending used by stdout and stderr. Classes that implement Stdout must define the lineTerminator field. The default semantics of stdout and stderr are not changed.
Deprecates FileSystemDeleteEvent.isDirectory, which always returns false.

`dart:js_interop`

Fixes an issue with several comparison operators in JSAnyOperatorExtension that were declared to return JSBoolean but really returned bool. This led to runtime errors when trying to use the return values. The implementation now returns a JSBoolean to align with the interface. See issue #55024 for more details.
Added ExternalDartReference and related conversion functions toExternalReference and toDartObject. This is a faster alternative to JSBoxedDartObject, but with fewer safety guarantees and fewer interoperability capabilities. See #55187 for more details.
On dart2wasm, JSBoxedDartObject now is an actual JS object that wraps the opaque Dart value instead of only externalizing the value. Like the JS backends, you'll now get a more useful error when trying to use it in another Dart runtime.
Added isA helper to make type checks easier with interop types. See #54138 for more details.

`dart:typed_data`

BREAKING CHANGE #53218 #53785: The unmodifiable view classes for typed data are deprecated.

To create an unmodifiable view of a typed-data object, use the asUnmodifiableView() methods added in Dart 3.3:
```
Uint8List data = ...;
final readOnlyView = data.asUnmodifiableView();
// readOnlyView has type Uint8List, and throws if attempted modified.
```
The reason for this change is to allow more flexibility in the implementation of typed data, so the native and web platforms can use different strategies to ensure that typed data has good performance.

The deprecated types will be removed in Dart 3.5.

Tools

Analyzer

Improved code completion. Fixed over 50% of completion correctness bugs, tagged analyzer-completion-correctness in the issue tracker.
Support for new annotations introduced in version 1.14.0 of the meta package.
- Support for the @doNotSubmit annotation, noting that any usage of an annotated member should not be submitted to source control.
- Support for the @mustBeConst annotation, which indicates that an annotated parameter only accepts constant arguments.

Linter

Added the unnecessary_library_name lint.
Added the missing_code_block_language_in_doc_comment lint.

Compilers

The compilation environment will no longer pretend to contain entries with value "" for all dart.library.foo strings, where dart:foo is not an available library. Instead there will only be entries for the available libraries, like dart.library.core, where the value was, and still is, "true". This should have no effect on const bool.fromEnvironment(...) or const String.fromEnvironment(...) without a defaultValue argument, an argument which was always ignored previously. It changes the behavior of const bool.hasEnvironment(...) on such an input, away from always being true and therefore useless.

DevTools

Updated DevTools to version 2.33.0 from 2.31.1. To learn more, check out the release notes for versions 2.32.0 and 2.33.0.

Pub

Dependency resolution and dart pub outdated will now surface if a dependency is affected by a security advisory, unless the advisory is listed under a ignored_advisories section in the pubspec.yaml file. To learn more about pub's support for security advisories, visit dart.dev/go/pub-security-advisories.
path-dependencies inside git-dependencies are now resolved relative to the git repo.
All dart pub commands can now be run from any subdirectory of a project. Pub will find the first parent directory with a pubspec.yaml and operate relative it.
New command dart pub unpack that downloads a package from pub.dev and extracts it to a subfolder of the current directory.

This can be useful for inspecting the code, or playing with examples.

Dart Runtime

Dart VM flags and options can now be provided to any executable generated using dart compile exe via the DART_VM_OPTIONS environment variable. DART_VM_OPTIONS should be set to a list of comma-separated flags and options with no whitespace. Options that allow for multiple values to be provided as comma-separated values are not supported (e.g., --timeline-streams=Dart,GC,Compiler).

Example of a valid DART_VM_OPTIONS environment variable:
```
DART_VM_OPTIONS=--random_seed=42,--verbose_gc
```
Dart VM no longer supports external strings: Dart_IsExternalString, Dart_NewExternalLatin1String and Dart_NewExternalUTF16String functions are removed from Dart C API.

3.3.4 - 2024-04-17

This is a patch release that:

Fixes an issue with JS interop in dart2wasm where JS interop methods that used the enclosing library's @JS annotation were actually using the invocation's enclosing library's @JS annotation. (issue #55430).

3.3.3 - 2024-03-27

This is a patch release that:

Fixes an issue where dart vm crashed when running on pre-SSE41 older CPUs on Windows (issue #55211).

3.3.2 - 2024-03-20

This is a patch release that:

Fixes an issue in the CFE that placed some structural parameter references out of their context in the code restored from dill files, causing crashes in the incremental compiler whenever it restored a typedef from dill such that the typedef contained a generic function type on its right-hand side (issue #55158).
Fixes an issue in the CFE that prevented redirecting factories from being resolved in initializers of extension types (issue #55194).
Fixes an issues with VM's implementation of DateTime.timeZoneName on Windows, which was checking whether current date is in the summer or standard time rather than checking if the given moment is in the summer or standard time (issue #55240).

3.3.1 - 2024-03-06

This is a patch release that:

Fixes an issue in dart2js where object literal constructors in interop extension types would fail to compile without an @JS annotation on the library (issue #55057).
Disallows certain types involving extension types from being used as the operand of an await expression, unless the extension type itself implements Future (issue #55095).

3.3.0

Language

Dart 3.3 adds extension types to the language. To use them, set your package's SDK constraint lower bound to 3.3 or greater (sdk: '^3.3.0').

Extension types

An extension type wraps an existing type with a different, static-only interface. It works in a way which is in many ways similar to a class that contains a single final instance variable holding the wrapped object, but without the space and time overhead of an actual wrapper object.

Extension types are introduced by extension type declarations. Each such declaration declares a new named type (not just a new name for the same type). It declares a representation variable whose type is the representation type. The effect of using an extension type is that the representation (that is, the value of the representation variable) has the members declared by the extension type rather than the members declared by its "own" type (the representation type). Example:

extension type Meters(int value) {
  String get label => '${value}m';
  Meters operator +(Meters other) => Meters(value + other.value);
}

void main() {
  var m = Meters(42); // Has type `Meters`.
  var m2 = m + m; // OK, type `Meters`.
  // int i = m; // Compile-time error, wrong type.
  // m.isEven; // Compile-time error, no such member.
  assert(identical(m, m.value)); // Succeeds.
}

The declaration Meters is an extension type that has representation type int. It introduces an implicit constructor Meters(int value); and a getter int get value. m and m.value is the very same object, but m has type Meters and m.value has type int. The point is that m has the members of Meters and m.value has the members of int.

Extension types are entirely static, they do not exist at run time. If o is the value of an expression whose static type is an extension type E with representation type R, then o is just a normal object whose run-time type is a subtype of R, exactly like the value of an expression of type R. Also the run-time value of E is R (for example, E == R is true). In short: At run time, an extension type is erased to the corresponding representation type.

A method call on an expression of an extension type is resolved at compile-time, based on the static type of the receiver, similar to how extension method calls work. There is no virtual or dynamic dispatch. This, combined with no memory overhead, means that extension types are zero-cost wrappers around their representation value.

While there is thus no performance cost to using extension types, there is a safety cost. Since extension types are erased at compile time, run-time type tests on values that are statically typed as an extension type will check the type of the representation object instead, and if the type check looks like it tests for an extension type, like is Meters, it actually checks for the representation type, that is, it works exactly like is int at run time. Moreover, as mentioned above, if an extension type is used as a type argument to a generic class or function, the type variable will be bound to the representation type at run time. For example:

void main() {
  var meters = Meters(3);

  // At run time, `Meters` is just `int`.
  print(meters is int); // Prints "true".
  print(<Meters>[] is List<int>); // Prints "true".

  // An explicit cast is allowed and succeeds as well:
  List<Meters> meterList = <int>[1, 2, 3] as List<Meters>;
  print(meterList[1].label); // Prints "2m".
}

Extension types are useful when you are willing to sacrifice some run-time encapsulation in order to avoid the overhead of wrapping values in instances of wrapper classes, but still want to provide a different interface than the wrapped object. An example of that is interop, where you may have data that are not Dart objects to begin with (for example, raw JavaScript objects when using JavaScript interop), and you may have large collections of objects where it's not efficient to allocate an extra object for each element.

Other changes

Breaking Change #54056: The rules for private field promotion have been changed so that an abstract getter is considered promotable if there are no conflicting declarations. There are no conflicting declarations if there are no non-final fields, external fields, concrete getters, or noSuchMethod forwarding getters with the same name in the same library. This makes the implementation more consistent and allows type promotion in a few rare scenarios where it wasn't previously allowed. It is unlikely, but this change could cause a breakage by changing an inferred type in a way that breaks later code. For example:
```
class A {
  int? get _field;
}
class B extends A {
  final int? _field;
  B(this._field);
}
test(A a) {
  if (a._field != null) {
    var x = a._field; // Previously had type `int?`; now has type `int`
    ...
    x = null; // Previously allowed; now causes a compile-time error.
  }
}
```
Affected code can be fixed by adding an explicit type annotation. For example, in the above snippet, var x can be changed to int? x.

It's also possible that some continuous integration configurations might fail if they have been configured to treat warnings as errors, because the expanded type promotion could lead to one of the following warnings:
- unnecessary_non_null_assertion
- unnecessary_cast
- invalid_null_aware_operator
These warnings can be addressed in the usual way, by removing the unnecessary operation in the first two cases, or changing ?. to . in the third case.

To learn more about other rules surrounding type promotion, check out the guide on Fixing type promotion failures.

Libraries

`dart:core`

String.fromCharCodes now allow start and end to be after the end of the Iterable argument, just like skip and take does on an Iterable.

`dart:ffi`

In addition to functions, @Native can now be used on fields.
Allow taking the address of native functions and fields via Native.addressOf.
The elementAt pointer arithmetic extension methods on core Pointer types are now deprecated. Migrate to the new - and + operators instead.
The experimental and deprecated @FfiNative annotation has been removed. Usages should be updated to use the @Native annotation.

`dart:js_interop`

Breaking Change in the representation of JS types #52687: JS types like JSAny were previously represented using a custom erasure of @staticInterop types that were compiler-specific. They are now represented as extension types where their representation types are compiler-specific. This means that user-defined @staticInterop types that implemented JSAny or JSObject can no longer do so and need to use JSObject.fromInteropObject. Going forward, it's recommended to use extension types to define interop APIs. Those extension types can still implement JS types.
JSArray and JSPromise generics: JSArray and JSPromise are now generic types whose type parameter is a subtype of JSAny?. Conversions to and from these types are changed to account for the type parameters of the Dart or JS type, respectively.
Breaking Change in names of extensions: Some dart:js_interop extension members are moved to different extensions on the same type or a supertype to better organize the API surface. See JSAnyUtilityExtension and JSAnyOperatorExtension for the new extensions. This shouldn't make a difference unless the extension names were explicitly used.
Add importModule to allow users to dynamically import modules using the JS import() expression.

`dart:js_interop_unsafe`

Add has helper to make hasProperty calls more concise.

`dart:typed_data`

BREAKING CHANGE (#53218) The unmodifiable view classes for typed data are deprecated. Instead of using the constructors for these classes to create an unmodifiable view, e.g.
```
Uint8List data = ...
final readOnlyView = UnmodifiableUint8ListView(data);
```
use the new asUnmodifiableView() methods:
```
Uint8List data = ...
final readOnlyView = data.asUnmodifiableView();
```
The reason for this change is to allow more flexibility in the implementation of typed data so the native and web platforms can use different strategies for ensuring typed data has good performance.

The deprecated types will be removed in a future Dart version.

`dart:nativewrappers`

Breaking Change #51896: The NativeWrapperClasses are marked base so that none of their subtypes can be implemented. Implementing subtypes can lead to crashes when passing such native wrapper to a native call, as it will try to unwrap a native field that doesn't exist.

Tools

Dart command line

The dart create command now uses v3 of package:lints, including multiple new recommended lints by default. To learn more about the updated collection of lints, check out the package:lints 3.0.0 changelog entry.

DevTools

Updated DevTools to version 2.31.1 from 2.28.1. To learn more, check out the release notes for versions 2.29.0, 2.30.0, and 2.31.0.

Wasm compiler (dart2wasm)

Breaking Change #54004: dart:js_util, package:js, and dart:js are now disallowed from being imported when compiling with dart2wasm. Prefer using dart:js_interop and dart:js_interop_unsafe.

Development JavaScript compiler (DDC)

Type arguments of package:js interop types are now printed as any instead of being omitted. This is simply a change to the textual representation of package js types that have type arguments. These type arguments are still completely ignored by the type system at runtime.
Removed "implements <...>" text from the Chrome custom formatter display for Dart classes. This information provides little value and keeping it imposes an unnecessary maintenance cost.

Production JavaScript compiler (dart2js)

Breaking Change #54201: The Invocation that is passed to noSuchMethod will no longer have a minified memberName, even when dart2js is invoked with --minify. See #54201 for more details.

Analyzer

You can now suppress diagnostics in pubspec.yaml files by adding an # ignore: <diagnostic_id> comment.
Invalid dart doc comment directives are now reported.
The flutter_style_todos lint now has a quick fix.

Linter

Removed the iterable_contains_unrelated_type and list_remove_unrelated_type lints. Consider migrating to the expanded collection_methods_unrelated_type lint.
Removed various lints that are no longer necessary with sound null safety:
- always_require_non_null_named_parameters
- avoid_returning_null,
- avoid_returning_null_for_future

3.2.3 - 2023-12-06

This is a patch release that:

Disallows final fields to be used in a constant context during analysis (issue #54232).
Upgrades Dart DevTools to version 2.28.4 (issue #54213).
Fixes new AOT snapshots in the SDK failing with SIGILL in ARM environments that don't support the integer division instructions or x86-64 environments that don't support SSE4.1 (issue #54215).

3.2.2 - 2023-11-29

This is a patch release that:

Adjusts the nullability computations in the implementation of the upper bound algorithm in the compiler frontend (issue #53999).
Fixes missing closure code completion entries for function parameters for LSP-based editors like VS Code (issue #54112).

3.2.1 - 2023-11-22

This is a patch release that:

Fixes the left/mobile sidebar being empty on non-class pages in documentation generated with dart doc (issue #54073).
Fixes a JSON array parsing bug that causes a segmentation fault when flutter test is invoked with the --coverage flag (SDK issue #54059, Flutter issue #124145).
Upgrades Dart DevTools to version 2.28.3 (issue #54085).

3.2.0 - 2023-11-15

Language

Dart 3.2 adds the following features. To use them, set your package's SDK constraint lower bound to 3.2 or greater (sdk: '^3.2.0').

Private field promotion: In most circumstances, the types of private final fields can now be promoted by null checks and is tests. For example:
```
class Example {
  final int? _privateField;
  Example(this._privateField);

  f() {
    if (_privateField != null) {
      // _privateField has now been promoted; you can use it without
      // null checking it.
      int i = _privateField; // OK
    }
  }
}

// Private field promotions also work from outside of the class:
f(Example x) {
  if (x._privateField != null) {
    int i = x._privateField; // OK
  }
}
```
To ensure soundness, a field is not eligible for field promotion in the following circumstances:
- If it's not final (because a non-final field could be changed in between the test and the usage, invalidating the promotion).
- If it's overridden elsewhere in the library by a concrete getter or a non-final field (because an access to an overridden field might resolve at runtime to the overriding getter or field).
- If it's not private (because a non-private field might be overridden elsewhere in the program).
- If it has the same name as a concrete getter or a non-final field in some other unrelated class in the library (because a class elsewhere in the program might extend one of the classes and implement the other, creating an override relationship between them).
- If there is a concrete class C in the library whose interface contains a getter with the same name, but C does not have an implementation of that getter (such unimplemented getters aren't safe for field promotion, because they are implicitly forwarded to noSuchMethod, which might not return the same value each time it's called).
Breaking Change #53167: Use a more precise split point for refutable patterns. Previously, in an if-case statement, if flow analysis could prove that the scrutinee expression was guaranteed to throw an exception, it would sometimes fail to propagate type promotions implied by the pattern to the (dead) code that follows. This change makes the type promotion behavior of if-case statements consistent regardless of whether the scrutinee expression throws an exception.

No live code is affected by this change, but there is a small chance that the change in types will cause a compile-time error to appear in some dead code in the user's project, where no compile-time error appeared previously.

Libraries

`dart:async`

Added broadcast parameter to Stream.empty constructor.

`dart:cli`

Breaking change #52121:
- waitFor is disabled by default and slated for removal in 3.4. Attempting to call this function will now throw an exception. Users that still depend on waitFor can enable it by passing --enable_deprecated_wait_for flag to the VM.

`dart:convert`

Breaking change #52801:
- Changed return types of utf8.encode() and Utf8Codec.encode() from List<int> to Uint8List.

`dart:developer`

Deprecated the Service.getIsolateID method.
Added getIsolateId method to Service.
Added getObjectId method to Service.

`dart:ffi`

Added the NativeCallable.isolateLocal constructor. This creates NativeCallables with the same functionality as Pointer.fromFunction, except that NativeCallable accepts closures.
Added the NativeCallable.keepIsolateAlive method, which determines whether the NativeCallable keeps the isolate that created it alive.
All NativeCallable constructors can now accept closures. Previously NativeCallables had the same restrictions as Pointer.fromFunction, and could only create callbacks for static functions.
Breaking change #53311: NativeCallable.nativeFunction now throws an error if is called after the NativeCallable has already been closed. Calls to close after the first are now ignored.

`dart:io`

Breaking change #53005: The headers returned by HttpClientResponse.headers and HttpRequest.headers no longer include trailing whitespace in their values.
Breaking change #53227: Folded headers values returned by HttpClientResponse.headers and HttpRequest.headers now have a space inserted at the fold point.

`dart:isolate`

Added Isolate.packageConfigSync and Isolate.resolvePackageUriSync APIs.

`dart:js_interop`

Breaking Change on JSNumber.toDart and Object.toJS: JSNumber.toDart is removed in favor of toDartDouble and toDartInt to make the type explicit. Object.toJS is also removed in favor of Object.toJSBox. Previously, this function would allow Dart objects to flow into JS unwrapped on the JS backends. Now, there's an explicit wrapper that is added and unwrapped via JSBoxedDartObject.toDart. Similarly, JSExportedDartObject is renamed to JSBoxedDartObject and the extensions ObjectToJSExportedDartObject and JSExportedDartObjectToObject are renamed to ObjectToJSBoxedDartObject and JSBoxedDartObjectToObject in order to avoid confusion with @JSExport.
Type parameters in external APIs: Type parameters must now be bound to a static interop type or one of the dart:js_interop types like JSNumber when used in an external API. This only affects dart:js_interop classes and not package:js or other forms of JS interop.
Subtyping dart:js_interop types: @staticInterop types can subtype only JSObject and JSAny from the set of JS types in dart:js_interop. Subtyping other types from dart:js_interop would result in confusing type errors before, so this makes it a static error.
Global context of dart:js_interop and @staticInterop APIs: Static interop APIs will now use the same global context as non-static interop instead of globalThis to avoid a greater migration. Static interop APIs, either through dart:js_interop or the @staticInterop annotation, have used JavaScript's globalThis as the global context. This is relevant to things like external top-level members or external constructors, as this is the root context we expect those members to reside in. Historically, this was not the case in dart2js and DDC. We used either self or DDC's global in non-static interop APIs with package:js. So, static interop APIs will now use one of those global contexts. Functionally, this should matter in only a very small number of cases, like when using older browser versions. dart:js_interop's globalJSObject is also renamed to globalContext and returns the global context used in the lowerings.
Breaking Change on Types of dart:js_interop External APIs: External JS interop APIs when using dart:js_interop are restricted to a set of allowed types. Namely, this includes the primitive types like String, JS types from dart:js_interop, and other static interop types (either through @staticInterop or extension types).
Breaking Change on dart:js_interop isNull and isUndefined: null and undefined can only be discerned in the JS backends. dart2wasm conflates the two values and treats them both as Dart null. Therefore, these two helper methods should not be used on dart2wasm and will throw to avoid potentially erroneous code.
Breaking Change on dart:js_interop typeofEquals and instanceof: Both APIs now return a bool instead of a JSBoolean. typeofEquals also now takes in a String instead of a JSString.
Breaking Change on dart:js_interop JSAny and JSObject: These types can only be implemented, and no longer extended, by user @staticInterop types.
Breaking Change on dart:js_interop JSArray.withLength: This API now takes in an int instead of JSNumber.

Tools

Development JavaScript compiler (DDC)

Applications compiled by DDC will no longer add members to the native JavaScript Object prototype.
Breaking change for JS interop with Symbols and BigInts: JavaScript Symbols and BigInts are now associated with their own interceptor and should not be used with package:js classes. These types were being intercepted with the assumption that they are a subtype of JavaScript's Object, but this is incorrect. This lead to erroneous behavior when using these types as Dart Objects. See #53106 for more details. Use dart:js_interop's JSSymbol and JSBigInt with extension types to interop with these types.

Production JavaScript compiler (dart2js)

Breaking change for JS interop with Symbols and BigInts: JavaScript Symbols and BigInts are now associated with their own interceptor and should not be used with package:js classes. These types were being intercepted with the assumption that they are a subtype of JavaScript's Object, but this is incorrect. This lead to erroneous behavior when using these types as Dart Objects. See #53106 for more details. Use dart:js_interop's JSSymbol and JSBigInt with extension types to interop with these types.

Dart command line

The dart create command has a new cli template to quickly create Dart command-line applications with basic argument parsing capabilities. To learn more about using the template, run dart help create.

Dart format

Always split enum declarations containing a line comment.
Fix regression in splitting type annotations with library prefixes.
Support --enable-experiment command-line option to enable language experiments.

DevTools

Incorporated the 2.26.1, 2.27.0, and 2.28.1 releases of DevTools.

Linter

Added the experimental annotate_redeclares lint.
Marked the use_build_context_synchronously lint as stable.

Pub

New option dart pub upgrade --tighten which will update dependencies' lower bounds in pubspec.yaml to match the current version.
The commands dart pub get/add/upgrade will now show if a dependency changed between direct, dev and transitive dependency.
The command dart pub upgrade no longer shows unchanged dependencies.

3.1.5 - 2023-10-25

This is a patch release that:

Fixes an issue affecting Dart compiled to JavaScript running in Node.js 21. A change in Node.js 21 affected the Dart Web compiler runtime. This patch release accommodates for those changes (issue #53810).

3.1.4 - 2023-10-18

This is a patch release that:

Fixes an issue in the Dart VM, users are not being able to see value of variables while debugging code (issue [#53747]).

3.1.3 - 2023-09-27

This is a patch release that:

Fixes a bug in dart2js which would cause the compiler to crash when using @staticInterop @anonymous factory constructors with type parameters (see issue #53579 for more details).
The standalone Dart VM now exports symbols only for the Dart_* embedding API functions, avoiding conflicts with other DSOs loaded into the same process, such as shared libraries loaded through dart:ffi, that may have different versions of the same symbols (issue [#53503]).
Fixes an issue with super slow access to variables while debugging. The fix avoids searching static functions in the imported libraries as references to members are fully resolved by the front-end. (issue #53541)

3.1.2 - 2023-09-13

This is a patch release that:

Fixes a bug in dart2js which crashed the compiler when a typed record pattern was used outside the scope of a function body, such as in a field initializer. For example final x = { for (var (int a,) in someList) a: a }; (issue #53449)
Fixes an expedient issue of users seeing an unhandled exception pause in the debugger, please see #53450 for more details. The fix uses try/catch in lookupAddresses instead of Future error so that we don't see an unhandled exception pause in the debugger (issue #53450)

3.1.1 - 2023-09-07

This is a patch release that:

Fixes a bug in the parser which prevented a record pattern from containing a nested record pattern, where the nested record pattern uses record destructuring shorthand syntax, for example final ((:a, :b), c) = record; (issue #53352).

3.1.0 - 2023-08-16

Libraries

`dart:async`

Breaking change #52334:
- Added the interface modifier to purely abstract classes: MultiStreamController, StreamConsumer, StreamIterator and StreamTransformer. As a result, these types can only be implemented, not extended or mixed in.

`dart:core`

Uri.base on native platforms now respects IOOverrides overriding current directory (#39796).

`dart:ffi`

Added the NativeCallable class, which can be used to create callbacks that allow native code to call into Dart code from any thread. See NativeCallable.listener. In future releases, NativeCallable will be updated with more functionality, and will become the recommended way of creating native callbacks for all use cases, replacing Pointer.fromFunction.

`dart:io`

Breaking change #51486:
- Added sameSite to the Cookie class.
- Added class SameSite.
Breaking change #52027: FileSystemEvent is sealed. This means that FileSystemEvent cannot be extended or implemented.
Added a deprecation warning when Platform is instantiated.
Added Platform.lineTerminator which exposes the character or characters that the operating system uses to separate lines of text, e.g., "\r\n" on Windows.

`dart:js_interop`

Object literal constructors: ObjectLiteral is removed from dart:js_interop. It's no longer needed in order to declare an object literal constructor with inline classes. As long as an external constructor has at least one named parameter, it'll be treated as an object literal constructor. If you want to create an object literal with no named members, use {}.jsify().

Other libraries

`package:js`

Breaking change to @staticInterop and external extension members: external @staticInterop members and external extension members can no longer be used as tear-offs. Declare a closure or a non-external method that calls these members, and use that instead.
Breaking change to @staticInterop and external extension members: external @staticInterop members and external extension members will generate slightly different JS code for methods that have optional parameters. Whereas before, the JS code passed in the default value for missing optionals, it will now pass in only the provided members. This aligns with how JS parameters work, where omitted parameters are actually omitted. For example, calling external void foo([int a, int b]) as foo(0) will now result in foo(0), and not foo(0, null).

Tools

DevTools

Incorporated the 2.24.0 and 2.25.0 releases of DevTools.

Linter

Added new static analysis lints you can enable in your package's analysis_options.yaml file:
- no_self_assignments
- no_wildcard_variable_uses

3.0.7 - 2023-07-26

This is a patch release that:

Fixes a bug in dart2js which would cause certain uses of records to lead to bad codegen causing a TypeError or NoSuchMethodError to be thrown at runtime (issue #53001).

3.0.6 - 2023-07-12

This is a patch release that:

Fixes a flow in flow analysis that causes it to sometimes ignore destructuring assignments (issue #52767).
Fixes an infinite loop in some web development compiles that include is or as expressions involving record types with named fields (issue #52869).
Fixes a memory leak in Dart analyzer's file-watching (issue #52791).
Fixes a memory leak of file system watcher related data structures (issue #52793).

3.0.5 - 2023-06-14

This is a patch release that:

Fixes a bad cast in the frontend which can manifest as a crash in the dart2js ListFactorySpecializer during Flutter web builds (issue #52403).

3.0.4 - 2023-06-07

This is a patch release that:

dart format now handles formatting nullable record types with no fields (dart_style issue #1224).
Fixes error when using records when targeting the web in development mode (issue #52480).

3.0.3 - 2023-02-07

This is a patch release that:

Fixes an AOT compiler crash when generating an implicit getter returning an unboxed record (issue #52449).
Fixes a situation in which variables appearing in multiple branches of an or-pattern might be erroneously reported as being mismatched (issue #52373).
Adds missing interface modifiers on the purely abstract classes MultiStreamController, StreamConsumer, StreamIterator and StreamTransformer (issue #52334).
Fixes an error during debugging when InternetAddress.tryParse is used (issue #52423).
Fixes a VM issue causing crashes on hot reload (issue #126884).
Improves linter support (issue #4195).
Fixes an issue in variable patterns preventing users from expressing a pattern match using a variable or wildcard pattern with a nullable record type (issue #52439).
Updates warnings and provide instructions for updating the Dart pub cache on Windows (issue #52386).

3.0.2 - 2023-05-24

This is a patch release that:

Fixes a dart2js crash when using a switch case expression on a record where the fields don't match the cases (issue #52438).
Add class modifier chips on class and mixin pages generated with dart doc (issue #3392).
Fixes a situation causing the parser to fail resulting in an infinite loop leading to higher memory usage (issue #52352).
Add clear errors when mixing inheritance in pre and post Dart 3 libraries (issue: #52078).

3.0.1 - 2023-05-17

This is a patch release that:

Fixes a compiler crash involving redirecting factories and FFI (issue #124369).
Fixes a dart2js crash when using a combination of local functions, generics, and records (issue #51899).
Fixes incorrect error using a void in a switch case expression (issue #52191).
Fixes a false error when using in switch case expressions when the switch refers to a private getter (issue #52041).
Prevent the use of when and as as variable names in patterns (issue #52260).
Fixes an inconsistency in type promotion between the analyzer and VM (issue #52241).
Improve performance on functions with many parameters (issue #1212).

3.0.0 - 2023-05-10

Language

Dart 3.0 adds the following features. To use them, set your package's SDK constraint lower bound to 3.0 or greater (sdk: '^3.0.0').

Records: Records are anonymous immutable data structures that let you aggregate multiple values together, similar to tuples in other languages. With records, you can return multiple values from a function, create composite map keys, or use them any other place where you want to bundle a couple of objects together.

For example, using a record to return two values:
```
(double x, double y) geoLocation(String name) {
  if (name == 'Nairobi') {
    return (-1.2921, 36.8219);
  } else {
    ...
  }
}
```
Pattern matching: Expressions build values out of smaller pieces. Conversely, patterns are an expressive tool for decomposing values back into their constituent parts. Patterns can call getters on an object, access elements from a list, pull fields out of a record, etc. For example, we can destructure the record from the previous example like so:
```
var (lat, long) = geoLocation('Nairobi');
print('Nairobi is at $lat, $long.');
```
Patterns can also be used in switch cases. There, you can destructure values and also test them to see if they have a certain type or value:
```
switch (object) {
  case [int a]:
    print('A list with a single integer element $a');
  case ('name', _):
    print('A two-element record whose first field is "name".');
  default: print('Some other object.');
}
```
Also, as you can see, non-empty switch cases no longer need break; statements.

Breaking change: Dart 3.0 interprets switch cases as patterns instead of constant expressions. Most constant expressions found in switch cases are valid patterns with the same meaning (named constants, literals, etc.). You may need to tweak a few constant expressions to make them valid. This only affects libraries that have upgraded to language version 3.0.

Switch expressions: Switch expressions allow you to use patterns and multi-way branching in contexts where a statement isn't allowed:

return TextButton(
  onPressed: _goPrevious,
  child: Text(switch (page) {
    0 => 'Exit story',
    1 => 'First page',
    _ when page == _lastPage => 'Start over',
    _ => 'Previous page',
  }),
);

If-case statements and elements: A new if construct that matches a value against a pattern and executes the then or else branch depending on whether the pattern matches:
```
if (json case ['user', var name]) {
  print('Got user message for user $name.');
}
```
There is also a corresponding if-case element that can be used in collection literals.
Sealed classes: When you mark a type sealed, the compiler ensures that switches on values of that type exhaustively cover every subtype. This enables you to program in an algebraic datatype style with the compile-time safety you expect:
```
sealed class Amigo {}
class Lucky extends Amigo {}
class Dusty extends Amigo {}
class Ned extends Amigo {}

String lastName(Amigo amigo) =>
    switch (amigo) {
      Lucky _ => 'Day',
      Ned _   => 'Nederlander',
    };
```
In this last example, the compiler reports an error that the switch doesn't cover the subclass Dusty.
Class modifiers: New modifiers final, interface, base, and mixin on class and mixin declarations let you control how the type can be used. By default, Dart is flexible in that a single class declaration can be used as an interface, a superclass, or even a mixin. This flexibility can make it harder to evolve an API over time without breaking users. We mostly keep the current flexible defaults, but these new modifiers give you finer-grained control over how the type can be used.

Breaking change: Class declarations from libraries that have been upgraded to Dart 3.0 can no longer be used as mixins by default. If you want the class to be usable as both a class and a mixin, mark it mixin class. If you want it to be used only as a mixin, make it a mixin declaration. If you haven't upgraded a class to Dart 3.0, you can still use it as a mixin.
Breaking change #50902: Dart reports a compile-time error if a continue statement targets a label that is not a loop (for, do and while statements) or a switch member. Fix this by changing the continue to target a valid labeled statement.
Breaking change language/#2357: Starting in language version 3.0, Dart reports a compile-time error if a colon (:) is used as the separator before the default value of an optional named parameter. Fix this by changing the colon (:) to an equal sign (=).

Libraries

General changes

Breaking Change: Non-mixin classes in the platform libraries can no longer be mixed in, unless they are explicitly marked as mixin class. The following existing classes have been made mixin classes:
- Iterable
- IterableMixin (now alias for Iterable)
- IterableBase (now alias for Iterable)
- ListMixin
- SetMixin
- MapMixin
- LinkedListEntry
- StringConversionSink

`dart:core`

Added bool.parse and bool.tryParse static methods.
Added DateTime.timestamp() constructor to get current time as UTC.
The type of RegExpMatch.pattern is now RegExp, not just Pattern.
Breaking change #49529:
- Removed the deprecated List constructor, as it wasn't null safe. Use list literals (e.g. [] for an empty list or <int>[] for an empty typed list) or List.filled.
- Removed the deprecated onError argument on int.parse, double.parse, and num.parse. Use the tryParse method instead.
- Removed the deprecated proxy and Provisional annotations. The original proxy annotation has no effect in Dart 2, and the Provisional type and provisional constant were only used internally during the Dart 2.0 development process.
- Removed the deprecated Deprecated.expires getter. Use Deprecated.message instead.
- Removed the deprecated CastError error. Use TypeError instead.
- Removed the deprecated FallThroughError error. The kind of fall-through previously throwing this error was made a compile-time error in Dart 2.0.
- Removed the deprecated NullThrownError error. This error is never thrown from null safe code.
- Removed the deprecated AbstractClassInstantiationError error. It was made a compile-time error to call the constructor of an abstract class in Dart 2.0.
- Removed the deprecated CyclicInitializationError. Cyclic dependencies are no longer detected at runtime in null safe code. Such code will fail in other ways instead, possibly with a StackOverflowError.
- Removed the deprecated NoSuchMethodError default constructor. Use the NoSuchMethodError.withInvocation named constructor instead.
- Removed the deprecated BidirectionalIterator class. Existing bidirectional iterators can still work, they just don't have a shared supertype locking them to a specific name for moving backwards.
Breaking change when migrating code to Dart 3.0: Some changes to platform libraries only affect code when that code is migrated to language version 3.0.
- The Function type can no longer be implemented, extended or mixed in. Since Dart 2.0 writing implements Function has been allowed for backwards compatibility, but it has not had any effect. In Dart 3.0, the Function type is final and cannot be subtyped, preventing code from mistakenly assuming it works.
- The following declarations can only be implemented, not extended:
  - Comparable
  - Exception
  - Iterator
  - Pattern
  - Match
  - RegExp
  - RegExpMatch
  - StackTrace
  - StringSink
  None of these declarations contained any implementation to inherit, and are marked as interface to signify that they are only intended as interfaces.
- The following declarations can no longer be implemented or extended:
  - MapEntry
  - OutOfMemoryError
  - StackOverflowError
  - Expando
  - WeakReference
  - Finalizer
  The MapEntry value class is restricted to enable later optimizations. The remaining classes are tightly coupled to the platform and not intended to be subclassed or implemented.

`dart:async`

Added extension member wait on iterables and 2-9 tuples of futures.
Breaking change #49529:
- Removed the deprecated DeferredLibrary class. Use the deferred as import syntax instead.

`dart:collection`

Added extension members nonNulls, firstOrNull, lastOrNull, singleOrNull, elementAtOrNull and indexed on Iterables. Also exported from dart:core.
Deprecated the HasNextIterator class (#50883).
Breaking change when migrating code to Dart 3.0: Some changes to platform libraries only affect code when it is migrated to language version 3.0.
- The following interface can no longer be extended, only implemented:
  - Queue
- The following implementation classes can no longer be implemented:
  - LinkedList
  - LinkedListEntry
- The following implementation classes can no longer be implemented or extended:
  - HasNextIterator (Also deprecated.)
  - HashMap
  - LinkedHashMap
  - HashSet
  - LinkedHashSet
  - DoubleLinkedQueue
  - ListQueue
  - SplayTreeMap
  - SplayTreeSet

`dart:developer`

Breaking change #49529:
- Removed the deprecated MAX_USER_TAGS constant. Use maxUserTags instead.
Callbacks passed to registerExtension will be run in the zone from which they are registered.
Breaking change #50231:
- Removed the deprecated Metrics, Metric, Counter, and Gauge classes as they have been broken since Dart 2.0.

`dart:ffi`

The experimental @FfiNative annotation is now deprecated. Usages should be replaced with the new @Native annotation.

`dart:html`

Breaking change: As previously announced, the deprecated registerElement and registerElement2 methods in Document and HtmlDocument have been removed. See #49536 for details.

`dart:math`

Breaking change when migrating code to Dart 3.0: Some changes to platform libraries only affect code when it is migrated to language version 3.0.
- The Random interface can only be implemented, not extended.

`dart:io`

Added name and signalNumber to the ProcessSignal class.
Deprecate NetworkInterface.listSupported. Has always returned true since Dart 2.3.
Finalize httpEnableTimelineLogging parameter name transition from enable to enabled. See #43638.
Favor IPv4 connections over IPv6 when connecting sockets. See #50868.
Breaking change #51035:
- Update NetworkProfiling to accommodate new String ids that are introduced in vm_service:11.0.0

`dart:js_util`

Added several helper functions to access more JavaScript operators, like delete and the typeof functionality.
jsify is now permissive and has inverse semantics to dartify.
jsify and dartify both handle types they understand natively more efficiently.
Signature of callMethod has been aligned with the other methods and now takes Object instead of String.

Tools

Observatory

Observatory is no longer served by default and users should instead use Dart DevTools. Users requiring specific functionality in Observatory should set the --serve-observatory flag.

Web Dev Compiler (DDC)

Removed deprecated command line flags -k, --kernel, and --dart-sdk.
The compile time flag --nativeNonNullAsserts, which ensures web library APIs are sound in their nullability, is by default set to true in sound mode. For more information on the flag, see NATIVE_NULL_ASSERTIONS.md.

dart2js

The compile time flag --native-null-assertions, which ensures web library APIs are sound in their nullability, is by default set to true in sound mode, unless -O3 or higher is passed, in which case they are not checked. For more information on the flag, see NATIVE_NULL_ASSERTIONS.md.

Dart2js

Cleanup related to #46100: the internal dart2js snapshot fails unless it is called from a supported interface, such as dart compile js, flutter build, or build_web_compilers. This is not expected to be a visible change.

Formatter

Format sync* and async* functions with => bodies.
Don't split after < in collection literals.
Better indentation of multiline function types inside type argument lists.
Fix bug where parameter metadata wouldn't always split when it should.

Analyzer

Most static analysis "hints" are converted to be "warnings," and any remaining hints are intended to be converted soon after the Dart 3.0 release. This means that any (previously) hints reported by dart analyze are now considered "fatal" (will result in a non-zero exit code). The previous behavior, where such hints (now warnings) are not fatal, can be achieved by using the --no-fatal-warnings flag. This behavior can also be altered, on a code-by-code basis, by changing the severity of rules in an analysis options file.
Add static enforcement of the SDK-only @Since annotation. When code in a package uses a Dart SDK element annotated with @Since, analyzer will report a warning if the package's Dart SDK constraint allows versions of Dart which don't include that element.
Protects the Dart Analysis Server against extreme memory usage by limiting the number of plugins per analysis context to 1. (issue #50981).

Linter

Updates the Linter to 1.35.0, which includes changes that

add new lints:
- implicit_reopen
- unnecessary_breaks
- type_literal_in_constant_pattern
- invalid_case_patterns
update existing lints to support patterns and class modifiers
remove support for:
- enable_null_safety
- invariant_booleans
- prefer_bool_in_asserts
- prefer_equal_for_default_values
- super_goes_last
fix unnecessary_parenthesis false-positives with null-aware expressions.
fix void_checks to allow assignments of Future<dynamic>? to parameters typed FutureOr<void>?.
fix use_build_context_synchronously in if conditions.
fix a false positive for avoid_private_typedef_functions with generalized type aliases.
update unnecessary_parenthesis to detect some doubled parens.
update void_checks to allow returning Never as void.
update no_adjacent_strings_in_list to support set literals and for- and if-elements.
update avoid_types_as_parameter_names to handle type variables.
update avoid_positional_boolean_parameters to handle typedefs.
update avoid_redundant_argument_values to check parameters of redirecting constructors.
improve performance for prefer_const_literals_to_create_immutables.
update use_build_context_synchronously to check context properties.
improve unnecessary_parenthesis support for property accesses and method invocations.
update unnecessary_parenthesis to allow parentheses in more null-aware cascade contexts.
update unreachable_from_main to track static elements.
update unnecessary_null_checks to not report on arguments passed to Future.value or Completer.complete.
mark always_use_package_imports and prefer_relative_imports as incompatible rules.
update only_throw_errors to not report on Never-typed expressions.
update unnecessary_lambdas to not report with late final variables.
update avoid_function_literals_in_foreach_calls to not report with nullable- typed targets.
add new lint: deprecated_member_use_from_same_package which replaces the soft-deprecated analyzer hint of the same name.
update public_member_api_docs to not require docs on enum constructors.
update prefer_void_to_null to not report on as-expressions.

Migration tool removal

The null safety migration tool (dart migrate) has been removed. If you still have code which needs to be migrated to null safety, please run dart migrate using Dart version 2.19, before upgrading to Dart version 3.0.

Pub

To preserve compatibility with null-safe code pre Dart 3, Pub will interpret a language constraint indicating a language version of 2.12 or higher and an upper bound of <3.0.0 as <4.0.0.

For example >=2.19.2 <3.0.0 will be interpreted as >=2.19.2 <4.0.0.
dart pub publish will no longer warn about dependency_overrides. Dependency overrides only take effect in the root package of a resolution.
dart pub token add now verifies that the given token is valid for including in a header according to RFC 6750 section 2.1. This means they must contain only the characters: ^[a-zA-Z0-9._~+/=-]+$. Before a failure would happen when attempting to send the authorization header.
dart pub get and related commands will now by default also update the dependencies in the example folder (if it exists). Use --no-example to avoid this.
On Windows the PUB_CACHE has moved to %LOCALAPPDATA%, since Dart 2.8 the PUB_CACHE has been created in %LOCALAPPDATA% when one wasn't present. Hence, this only affects users with a PUB_CACHE created by Dart 2.7 or earlier. If you have path/to/.pub-cache/bin in PATH you may need to update your PATH.

2.19.6 - 2023-03-29

This is a patch release that:

Fixes an Out of Memory exception due to a VM bug. (issue #50537).

2.19.5 - 2023-03-22

This is a patch release that:

Fixes broken usage of Dart_CObject_Type. (issue #51459).

2.19.4 - 2023-03-08

This is a patch release that:

Fixes mobile devices vm crashes caused by particular use of RegExp. (issue #121270).

2.19.3 - 2023-03-01

This is a patch release that:

Updates DDC test and builder configuration. (issue #51481).
Protects the Dart Analysis Server against extreme memory usage by limiting the number of plugins per analysis context to 1. (issue #50981).

2.19.2 - 2023-02-08

This is a patch release that:

Fixes a VM crash when mixing the use of double and float calculations in debug/jit configuration. (issue #50622).
Fixes the compiler crashing when attempting to inline a method with lots of optional parameters with distinct default values. (issue #119220).
Fixes the part_of_different_library error encountered when using PackageBuildWorkspace. (issue #51087).

2.19.1 - 2023-02-01

This is a patch release that:

Fixes pub get behaviour: In Dart 2.19.0 a dart pub get with a pubspec.lock created by a 2.18 SDK will unlock all constraints, effectively like a pub upgrade (issue #51166).
Stops rewriting SDK constraints: In Dart 3, a SDK constraint like >=2.12.0 <3.0.0 gets interpreted by the pub client as >=2.12.0 <4.0.0 to allow for backwards compatibility (issue #51101).

This change was intended for Dart 3.0.0 and later, but was landed already in 2.19.0. It is now being removed in 2.19.1, as it can give confusing messages such as:

Because library requires SDK version >=2.19.2 <4.0.0, version solving failed.

This reinterpretation no longer happens in Dart 2.19.1.
Fixes a VM crash caused by incorrect sharing of RegExp between isolates (issue #51130).

2.19.0 - 2023-01-24

Language

Breaking change #49635: Flag additional code as unreachable due to types Null and Never. Several unusual constructs that lead to unreachable code are now recognized by flow analysis:
- Control flow after an expression of the form e ?? other or e ??= other, where e has static type Null and other has static type Never, is considered unreachable.
- Control flow predicated on an expression of the form e is Never evaluating to true is considered unreachable.
- Control flow predicated on an expression of the form e is! Never evaluating to false is considered unreachable.
- Control flow on the RHS of a null-aware access such as e?.property..., e?.property = ... or e?.method(...), where e has static type Null, is considered unreachable (Note: this can arise in the presence of extension methods).
Previously, these behaviors only took effect if e was a reference to a local variable.

Additionally, a type test of the form v is Never (where v is a local variable) no longer promotes v to type Never.

Breaking Change #49687: Don't delegate inaccessible private names to noSuchMethod. If a concrete class implements an interface containing a member with a name that's private to different library, and does not inherit an implementation of that interface member, a invocation of that member will result in an exception getting thrown. Previously, such attempts would result in the call being diverted to the noSuchMethod method.

This change closes a loophole in Dart's privacy system, where another library can provide a different implementation of a supposedly private member using noSuchMethod, and paves the way for a future implementation of promotion for private final fields (see #2020).

Breaking Change #50383: Report a compile-time error for all cyclic dependencies during top-level type inference.

Previously, some of these dependencies were ignored, based on an analysis determining that they could not influence the inferred type. However, this analysis was complex, differed slightly among tools, and had become much more complex due to other changes (especially, enhanced flow analysis).

With this change, all tools treat these cyclic dependencies in the same way, the analysis is well-understood, and, arguably, the code is more readable.

Breakage is mitigated by adding a declared type to one top-level declaration per cycle which is now an error.

Add support for unnamed libraries. Dart language 2.19 allows a library directive to be written without a name (library;). A library directive can be used for library-level annotations (such as @deprecated) and for library-level documentation comments, and with this new feature, you don't have to provide a unique name for each library directive. Instead, a name can simply be omitted (see #1073).

Libraries

`dart:convert`

Breaking change #34233: The previously deprecated API DEFAULT_BUFFER_SIZE in JsonUtf8Encoder has been removed.

`dart:core`

Deprecated FallThroughError. Has not been thrown since Dart 2.0 (see #49529).
Added copyWith extension method on DateTime (see [#24644]).
Deprecated RangeError.checkValidIndex in favor of IndexError.check.
Deprecated IndexError constructor in favor of IndexError.withLength constructor.
Deprecated NullThrownError and CyclicInitializationError. Neither error is thrown by null safe code. #49529: #49529 [#24644]: #24644

`dart:developer`

Breaking change #34233: The previously deprecated APIs kInvalidParams, kExtensionError, kExtensionErrorMax, and kExtensionErrorMin in ServiceExtensionResponse have been removed. They have been replaced by invalidParams, extensionError, extensionErrorMax, and extensionErrorMin.
Deprecated UserTag.MAX_USER_TAGS in favor of UserTag.maxUserTags.

`dart:ffi`

Breaking change #49935: The runtime type argument of Pointer has changed to Never in preparation of completely removing the runtime type argument. Pointer.toString has changed to not report any type argument.

`dart:html`

Add constructor and slice to SharedArrayBuffer.
Deprecated registerElement and registerElement2 in Document and HtmlDocument. These APIs were based on the deprecated Web Components v0.5 specification and are not supported by browsers today. These APIs are expected to be deleted in a future release. See the related breaking change request #49536.

`dart:io`

Breaking change #49305: Disallow negative or hexadecimal content-length headers.
Breaking change #49647: File.create now takes new optional exclusive bool parameter, and when it is true the operation will fail if target file already exists.
Breaking change #49878: Calling ResourceHandle.toFile(), ResourceHandle.toSocket(), ResourceHandle.toRawSocket() or ResourceHandle.toRawDatagramSocket(), more than once now throws a StateError.

The previous behavior would allow multiple Dart objects to refer to the same file descriptor, which would produce errors when one object was closed or garbage collected.

Adds three new FileSystemException subclasses to handle common error cases:
- PathAccessException: The necessary access rights are not available.
- PathExistsException: The path being created already exists.
- PathNotFoundException: The path being accessed does not exist.

`dart:isolate`

Add Isolate.run to run a function in a new isolate.
Breaking change: SendPort.send is again applying strict checks to the contents of the message when sending messages between isolates that are not known to share the same code (e.g. an isolate spawned via Isolate.spawnUri). These checks were accidentally relaxed in an earlier Dart version allowing all classes from dart:core and dart:collection through. This for example means that you can't send an instance of a HashMap to an isolate spawned via Isolate.spawnUri. See SendPort.send documentation for the full list of restrictions.

`dart:mirrors`

Breaking change #34233: The APIs MirrorsUsed and Comment have been removed. MirrorsUsed was experimental and deprecated; Comment was previously used internally in dart2js. Both are no longer functional.

Other libraries

`package:js`

Breaking changes to the preview feature @staticInterop:
- Classes with this annotation are now disallowed from using external generative constructors. Use external factorys for these classes instead, and the behavior should be identical. This includes use of synthetic constructors. See #48730 and #49941 for more details.
- Classes with this annotation's external extension members are now disallowed from using type parameters e.g. external void method<T>(T t). Use a non-external extension method for type parameters instead. See #49350 for more details.
- Classes with this annotation should also have the @JS annotation. You can also have the @anonymous annotation with these two annotations for an object literal constructor, but it isn't required.
- Classes with this annotation can not be implemented by classes without this annotation. This is to avoid confusing type behavior.

Tools

Analyzer

add static enforcement of new mustBeOverridden annotation, and quick fixes
add quick fixes for many diagnostics including compile-time errors, hints, and lints. There are now quick fixes for over 300 diagnostic codes. These lint rules have new fixes: combinators_ordering, dangling_library_doc_comments, implicit_call_tearoffs, library_annotations, and unnecessary_library_directive.
add new hints: body_might_complete_normally_catch_error, cast_from_null_always_fails, cast_from_nullable_always_fails, deprecated_colon_for_default_value, and duplicate_export
remove hint: invalid_override_different_default_values

Linter

Updated the Linter to 1.31.0, which includes changes that

add new lint: collection_methods_unrelated_type.
add new lint: combinators_ordering.
add new lint: dangling_library_doc_comments.
add new lint: enable_null_safety.
add new lint: implicit_call_tearoffs.
add new lint: library_annotations.
add new lint: unnecessary_library_directive.
add new lint: unreachable_from_main.
add new lint: use_string_in_part_of_directives.
fix no_leading_underscores_for_local_identifiers to not report super formals as local variables.
fix unnecessary_overrides false negatives.
fix cancel_subscriptions for nullable fields.
update library_names to support unnamed libraries.
fix unnecessary_parenthesis support for as-expressions.
fix use_build_context_synchronously to check for context property accesses.
fix false positive in comment_references.
improved unrelated type checks to handle enums and cascades.
fix unnecessary_brace_in_string_interps for this expressions .
update use_build_context_synchronously for BuildContext.mounted.
improve flutter_style_todos to handle more cases.
fix use_build_context_synchronously to check for BuildContexts in named expressions.
fix exhaustive_cases to check parenthesized expressions
update avoid_redundant_argument_values to work with enum declarations.
fix avoid_redundant_argument_values when referencing required parameters in legacy libraries.
fix use_super_parameters false positives with repeated super parameter references.
update use_late_for_private_fields_and_variables to handle enums.
fix prefer_contains false positives when a start index is non-zero.
improve noop_primitive_operations to catch .toString() in string interpolations.
update public_member_api_docs to report diagnostics on extension names (instead of bodies).
fix use_colored_box and use_decorated_box to not over-report on containers without a child.
fix unnecessary_parenthesis false positives on a map-or-set literal at the start of an expression statement.
fix prefer_final_locals false positives reporting on fields.
fix unnecessary_overrides to allow overrides on @Protectedmembers.
fix avoid_multiple_declarations_per_line false positives in for statements.
fix prefer_final_locals false positives on declaration lists with at least one non-final variable.
fixuse_build_context_synchronously to handle awaits in if conditions.
improves performance for:
- avoid_escaping_inner_quotes.
- avoid_null_checks_in_equality_operators.
- avoid_positional_boolean_parameters.
- avoid_returning_null.
- avoid_returning_null.
- avoid_returning_this.
- cascade_invocations.
- diagnostic_describe_all_properties.
- flutter_style_todos.
- join_return_with_statement.
- parameter_assignments.
- prefer_const_constructors.
- prefer_constructors_over_static_methods.
- prefer_constructors_over_static_methods.
- prefer_contains.
- prefer_foreach.
- prefer_interpolation_to_compose_strings.
- prefer_interpolation_to_compose_strings.
- recursive_getters.
- tighten_type_of_initializing_formals.
- unnecessary_lambdas.
- use_late_for_private_fields_and_variables.

Pub

Treats packages with sdk constraint lower bound >=2.12.0 or more and upper bound <3.0.0 as compatible with <4.0.0.
Introduces content-hashes in pubspec.lock, to protect against corrupted package repositories.

These will show up in the lock file on the first run of dart pub get.

See https://dart.dev/go/content-hashes for more details.
New flag dart pub get --enforce-lockfile will fetch dependencies, but fail if anything deviates from pubspec.lock. Useful for ensuring reproducible runs in CI and production.
Remove remaining support for .packages files. The flag --legacy-packages-file is no longer supported.
The client will now default to the pub.dev repository instead of pub.dartlang.org. This will cause a change in pubspec.lock.
Support a new field funding in pubspec.yaml.
Validate the CRC32c checksum of downloaded archives and retry on failure.
dart pub add foo:<constraint> with an existing dependency will now update the constraint rather than fail.
Update dart pub publish to allow dependency_overrides in pubspec.yaml. They will still cause a publication warning. Note that only dependency_overrides from the root package effect resolution.
Update dart pub publish to require a working resolution. If publishing a breaking release of mutually dependent packages use dependency_overrides to obtain a resolution.
dart pub add will now allow adding multiple packages from any source using the same YAML syntax as in pubspec.yaml.

For example:
```
$ dart pub add retry:^1.0.0 'dev:foo{"git":"https://github.com/foo/foo"}'
```
dart pub publish will now give a warning if dart analyze reports any diagnostics.
dart pub get now fails gracefully when run from inside the pub-cache.
dart pub publish now shows the file sizes of large files in your package to prevent accidental publication of large unrelated files.
Fix a bug in dart pub upgrade --major-versions where packages not requiring major updates would be held back unless needed.

dart2js

Breaking change 49473: dart2js no longer supports HTTP URIs as inputs.

2.18.5 - 2022-11-23

fixes an error on private variable setters in mixins on dart web (issue #50119).
fixes the handling of type parameter nullability in factory constructors (issue #50392).

2.18.4 - 2022-11-02

This is a patch release that fixes crashes during hot reload (issue flutter/flutter#113540).

2.18.3 - 2022-10-19

This is a patch release that fixes a regression in code coverage computation (issue #49887).

2.18.2 - 2022-09-28

This is a patch release that:

fixes incorrect behavior in Uri.parse.
fixes a compiler crash (issue #50052).

Libraries

`dart:core`

Security advisory CVE-2022-3095: There is a auth bypass vulnerability in Dart SDK, specifically dart:uri core library, used to parse and validate URLs. This library is vulnerable to the backslash-trick wherein backslash is not recognized as equivalent to forward slash in URLs.

The Uri class has been changed to parse a backslash in the path or the authority separator of a URI as a forward slash. This affects the Uri constructor's path parameter, and the Uri.parse method. This change was made to not diverge as much from the browser URL behavior. The Dart Uri class is still not an implementation of the same standard as the browser's URL implementation.

2.18.1 - 2022-09-14

This is a patch release that fixes a crash caused by incorrect type inference (issues flutter/flutter#110715 and flutter/flutter#111088).

2.18.0 - 2022-08-30

Language

The following features are new in the Dart 2.18 language version. To use them, you must set the lower bound on the SDK constraint for your package to 2.18 or greater (sdk: '>=2.18.0 <3.0.0').

Enhanced type inference for generic invocations with function literals: Invocations of generic methods/constructors that supply function literal arguments now have improved type inference. This primarily affects the Iterable.fold method. For example, in previous versions of Dart, the compiler would fail to infer an appropriate type for the parameter a:
```
void main() {
  List<int> ints = [1, 2, 3];
  var maximum = ints.fold(0, (a, b) => a < b ? b : a);
}
```
With this improvement, a receives its type from the initial value, 0.

On rare occasions, the wrong type will be inferred, leading to a compile-time error, for example in this code, type inference will infer that a has a type of Null:
```
void main() {
  List<int> ints = [1, 2, 3];
  var maximumOrNull = ints.fold(null,
      (a, b) => a == null || a < b ? b : a);
}
```
This can be worked around by supplying the appropriate type as an explicit type argument to fold:
```
void main() {
  List<int> ints = [1, 2, 3];
  var maximumOrNull = ints.fold<int?>(null,
      (a, b) => a == null || a < b ? b : a);
}
```

Breaking Change #48167: Mixin of classes that don't extend Object is no longer supported:
```
class Base {}
class Mixin extends Base {}
class C extends Base with Mixin {}
```
This should instead be written using a mixin declaration of Mixin:
```
class Base {}
mixin Mixin on Base {}
class C extends Base with Mixin {}
```
This feature has not been supported in most compilation targets for some time but is now completely removed.

Core libraries

`dart:async`

The Stream.fromIterable stream can now be listened to more than once.

`dart:collection`

Deprecates BidirectionalIterator.

`dart:core`

Allow omitting the unencodedPath positional argument to Uri.http and Uri.https to default to an empty path.

`dart:html`

Add connectionState attribute and connectionstatechange listener to RtcPeerConnection.

`dart:io`

Breaking Change #49045: The uri property of RedirectException in dart:io has been changed to be nullable. Programs must be updated to handle the null case.
Breaking Change #34218: Constants in dart:io's networking APIs following the SCREAMING_CAPS convention have been removed (they were previously deprecated). Please use the corresponding lowerCamelCase constants instead.
Breaking Change #45630: The Dart VM no longer automatically restores the initial terminal settings upon exit. Programs that change the Stdin settings lineMode and echoMode are now responsible for restoring the settings upon program exit. E.g. a program disabling echoMode will now need to restore the setting itself and handle exiting by the appropriate signals if desired:
```
import 'dart:io';
import 'dart:async';

main() {
  bool echoWasEnabled = stdin.echoMode;
  try {
    late StreamSubscription subscription;
    subscription = ProcessSignal.sigint.watch().listen((ProcessSignal signal) {
      stdin.echoMode = echoWasEnabled;
      subscription.cancel();
      Process.killPid(pid, signal); /* Die by the signal. */
    });
    stdin.echoMode = false;
  } finally {
    stdin.echoMode = echoWasEnabled;
  }
}
```
This change is needed to fix #36453 where the dart programs not caring about the terminal settings can inadvertently corrupt the terminal settings when e.g. piping into less.

Furthermore the echoMode setting now only controls the echo local mode and no longer sets the echonl local mode on POSIX systems (which controls whether newline are echoed even if the regular echo mode is disabled). The echonl local mode is usually turned off in common shell environments. Programs that wish to control the echonl local mode can use the new echoNewlineMode setting.

The Windows console code pages (if not UTF-8) and ANSI escape code support (if disabled) remain restored when the VM exits.

`dart:js_util`

Added dartify and a number of minor helper functions.

Dart VM

Implementation of async/async*/sync* is revamped in Dart VM, both in JIT and AOT modes. This also affects Flutter except Flutter Web.

Besides smaller code size and better performance of async methods, the new implementation carries a few subtle changes in behavior:

If async method returns before reaching the first await, it now returns a completed Future. Previously async methods completed resulting Future in separate microtasks.
Stack traces no longer have duplicate entries for async methods.
New implementation now correctly throws an error if null occurs as an argument of a logical expression (&& and ||) which also contains an await.
New implementation avoids unnecessary extending the liveness of local variables in async/async*/sync* methods, which means that unused objects stored in local variables in such methods might be garbage collected earlier than they were before (see issue #36983 for details).

Tools

General

Breaking Change #48272: The .packages file has been fully discontinued. Historically when the commands dart pub get or flutter pub get are executed, pub resolved all dependencies, and installs those dependencies to the local pub cache. It furthermore created a mapping from each used package to their location on the local file system, and wrote that into two files:
- .dart_tool/package_config.json
- .packages (deprecated in Dart 2.8.0)
As of Dart 2.18.0, the .packages is now fully desupported, and all tools distributed in, and based on, the Dart SDK no longer support it, and thus solely use the .dart_tool/package_config.json file. If you've run dart pub get or flutter pub get with any Dart SDK from the past few years you already have a .dart_tool/package_config.json and thus should not be impacted. You can delete any old .packages files.

If you have any third-party tools that for historical reasons depend on a .packages we will support the ability to generate a .packages by passing the flag --legacy-packages-file to dart pub get. This support will be removed in a following stable release.

Dart command line

Breaking change #46100: The standalone dart2js and dartdevc tools have been removed as previously announced. dart2js is replaced by the dart compile js command, dartdevc is no longer exposed as a command-line tool.
Breaking change #46100: The standalone dartanalyzer tool has been removed as previously announced. dartanalyzer is replaced by the dart analyze command.

Analyzer

added quick fixes for diagnostics: abstract_field_constructor_initializer, abstract_class_member, always_put_control_body_on_new_line, avoid_print, avoid_renaming_method_parameters, discarded_futures, enum_with_abstract_member, non_bool_condition, super_formal_parameter_without_associated_named, unawaited_futures, unnecessary_final unused_element_parameter,
added new Hint: deprecated_export_use

Linter

Updated the Linter to 1.25.0, which includes changes that

add new lint: discarded_futures.
add new lint: unnecessary_null_aware_operator_on_extension_on_nullable.
add new lint: unnecessary_to_list_in_spreads.
improve message and highlight range for no_duplicate_case_values
improve performance for lines_longer_than_80_chars, prefer_const_constructors_in_immutables, and prefer_initializing_formals.
fix prefer_final_parameters to support super parameters.
fix unawaited_futures to handle string interpolated futures.
update use_colored_box to not flag nullable colors,
fix no_leading_underscores_for_local_identifiers to lint local function declarations.
fix avoid_init_to_null to correctly handle super initializing defaults that are non-null.
update no_leading_underscores_for_local_identifiers to allow identifiers with just underscores.
fix flutter_style_todos to support usernames that start with a digit.
update require_trailing_commas to handle functions in asserts and multi-line strings.
update unsafe_html to allow assignments to img.src.
fix unnecessary_null_checks to properly handle map literal entries.

Pub

dart pub get and dart pub upgrade no longer create the .packages file. For details, see breaking change #48272 above.
dart pub outdated now shows which of your dependencies are discontinued.
dart pub publish will now list all the files it is about to publish.

2.17.7 - 2022-08-24

This is a patch release that:

fixes a crash in the debugger (issue #49209).

2.17.6 - 2022-07-13

This is a patch release that:

improves code completion for Flutter (issue #49054).
fixes a crash on ARM (issue #106510).
fixes a compiler crash with Finalizable parameters (issue #49402).

2.17.5 - 2022-06-22

This is a patch release that:

improves analysis of enums and switch (issue #49188).
fixes a compiler crash when initializing Finalizable objects (issue #49075).

2.17.3 - 2022-06-01

This is a patch release that fixes:

a Dart VM compiler crash (issue #100375).
code completion when writing method overrides (issue #49027).
the dart pub login command (issue #3424).
analysis of enhanced enums (issue #49097).

2.17.1 - 2022-05-18

This is a patch release that fixes:

an analyzer plugin crash (issue #48682).
Dart FFI support for late Finalizable variables (issue #49024).
dart compile on macOS 10.15 (issue #49010).

2.17.0 - 2022-05-11

Language

The following features are new in the Dart 2.17 language version. To use them, you must set the lower bound on the SDK constraint for your package to 2.17 or greater (sdk: '>=2.17.0 <3.0.0').

Enhanced enums with members: Enum declarations can now define members including fields, constructors, methods, getters, etc. For example:

enum Water {
  frozen(32),
  lukewarm(100),
  boiling(212);

  final int tempInFahrenheit;
  const Water(this.tempInFahrenheit);

  @override
  String toString() => "The $name water is $tempInFahrenheit F.";
}

Constructors must be const since enum values are always constants. If the constructor takes arguments, they are passed when the enum value is declared.

The above enum can be used like so:

void main() {
  print(Water.frozen); // prints "The frozen water is 32 F."
}

Super parameters: When extending a class whose constructor takes parameters, the subclass constructor needs to provide arguments for them. Often, these are passed as parameters to the subclass constructor, which then forwards them to the superclass constructor. This is verbose because the subclass constructor must list the name and type of each parameter in its parameter list, and then explicitly forward each one as an argument to the superclass constructor.

@roy-sianez suggested allowing super. before a subclass constructor parameter to implicitly forward it to the corresponding superclass constructor parameter. Applying this feature to Flutter eliminated nearly 2,000 lines of code. For example, before:
```
class CupertinoPage<T> extends Page<T> {
  const CupertinoPage({
    required this.child,
    this.maintainState = true,
    this.title,
    this.fullscreenDialog = false,
    LocalKey? key,
    String? name,
    Object? arguments,
    String? restorationId,
  }) : super(
        key: key,
        name: name,
        arguments: arguments,
        restorationId: restorationId,
      );

  // ...
}
```
And using super parameters:
```
class CupertinoPage<T> extends Page<T> {
  const CupertinoPage({
    required this.child,
    this.maintainState = true,
    this.title,
    this.fullscreenDialog = false,
    super.key,
    super.name,
    super.arguments,
    super.restorationId,
  });

  // ...
}
```
From our analysis, over 90% of explicit superclass constructor calls can be completely eliminated, using super. parameters instead.

Named args everywhere: In a function call, Dart requires positional arguments to appear before named arguments. This can be frustrating for arguments like collection literals and function expressions that look best as the last argument in the argument list but are positional, like the test() function in the test package:
```
main() {
  test('A test description', () {
    // Very long function body here...
  }, skip: true);
}
```
It would be better if the skip argument appeared at the top of the call to test() so that it wasn't easily overlooked, but since it's named and the test body argument is positional, skip must be placed at the end.

Dart 2.17 removes this restriction. Named arguments can be freely interleaved with positional arguments, allowing code like:
```
main() {
  test(skip: true, 'A test description', () {
    // Very long function body here...
  });
}
```

Core libraries

`dart:core`

Add Finalizer and WeakReference which can potentially detect when objects are "garbage collected".
Add isMimeType method to UriData class, to allow case-insensitive checking of the MIME type.
Add isCharset and isEncoding methods to UriData class, to allow case-insensitive and alternative-encoding-name aware checking of the MIME type "charset" parameter.
Make UriData.fromString and UriData.fromBytes recognize and omit a "text/plain" mimeType even if it is not all lower-case.

`dart:ffi`

Add ref= and []= methods to the StructPointer and UnionPointer extensions. They copy a compound instance into a native memory region.
Add AbiSpecificIntegers for common C types:
- char
- unsigned char
- signed char
- short
- unsigned short
- int
- unsigned int
- long
- unsigned long
- long long
- unsigned long long
- uintptr_t
- size_t
- wchar_t
Add NativeFinalizer which can potentially detect when objects are "garbage collected". NativeFinalizers run native code where dart:core's Finalizers run Dart code on finalization.

`dart:html`

Add scrollIntoViewIfNeeded to Element. Previously, this method was nested within scrollIntoView based on the ScrollAlignment value. scrollIntoView is unchanged for now, but users who intend to use the native Element.scrollIntoViewIfNeeded should use the new scrollIntoViewIfNeeded definition instead.
Change Performance.mark and Performance.measure to accept their different overloads. mark can now accept a markOptions map, and measure can now accept a startMark and endMark, or a measureOptions map. Both methods return their correct return types now as well - PerformanceEntry? and PerformanceMeasure?, respectively.

`dart:indexed_db`

IdbFactory.supportsDatabaseNames has been deprecated. It will always return false.

`dart:io`

Breaking Change #47887: HttpClient has a new connectionFactory property, which allows socket creation to be customized. Classes that implement HttpClient may be broken by this change. Add the following method to your classes to fix them:

void set connectionFactory(
    Future<ConnectionTask<Socket>> Function(
            Uri url, String? proxyHost, int? proxyPort)?
        f) =>
    throw UnsupportedError("connectionFactory not implemented");

Breaking Change #48093: HttpClient has a new keyLog property, which allows TLS keys to be logged for debugging purposes. Classes that implement HttpClient may be broken by this change. Add the following method to your classes to fix them:
```
void set keyLog(Function(String line)? callback) =>
    throw UnsupportedError("keyLog not implemented");
```
Breaking Change #34218: Constants in dart:io following the SCREAMING_CAPS convention have been removed (they were previously deprecated). Please use the corresponding lowerCamelCase constants instead.
Breaking Change #48513: Add a new allowLegacyUnsafeRenegotiation property to SecurityContext, which allows TLS renegotiation for client secure sockets.
Add a optional keyLog parameter to SecureSocket.connect and SecureSocket.startConnect.
Deprecate SecureSocket.renegotiate and RawSecureSocket.renegotiate, which were no-ops.

Tools

Dart command line

Breaking change #46100: The standalone dart2js tool has been marked deprecated as previously announced. Its replacement is the dart compile js command. Should you find any issues, or missing features, in the replacement command, kindly file an issue.
Breaking change #46100: The standalone dartdevc tool has been marked deprecated as previously announced and will be deleted in a future Dart stable release. This tool was intended for use only by build systems like bazel, build_web_compilers and flutter_tools. The functionality remains available for those systems, but it is no longer exposed as a command-line tool in the SDK. Please share any concerns in the breaking change tracking issue.
Breaking change #46100: The standalone dartdoc tool has been removed as previously announced. Its replacement is the dart doc command.
The template names used in the dart create command have been simplified, and the current template names are now the set shown below. (Note: for backwards compatibility the former template names can still be used.)

          [console] (default)    A command-line application.
          [package]              A package containing shared Dart libraries.
          [server-shelf]         A server app using package:shelf.
          [web]                  A web app that uses only core Dart libraries.

Analyzer

added quick fixes for diagnostics: always_use_package_imports, avoid_void_async, cascade_invocations, default_list_constructor, must_call_super, no_leading_underscores_for_local_identifiers, null_check_on_nullable_type_parameter, prefer_function_declarations_over_variables, sort_constructors_first, sort_unnamed_constructors_first, undefined_enum_constant, unnecessary_late, unnecessary_null_aware_assignments, use_enums, use_raw_strings, use_super_parameters, var_return_type
added many errors for invalid enhanced enums
added new Hint: unnecessary_final
added new FFI error: compound_implements_finalizable
improved errors for invalid Unicode escapes in source code

Linter

Updated the Linter to 1.22.0, which includes changes that

fixes null-safe variance exceptions in invariant_booleans.
updates depend_on_referenced_packages to treat flutter_gen as a virtual package, not needing an explicit dependency.
updates unnecessary_null_checks and null_check_on_nullable_type_parameter to handle list/set/map literals, and yield and await expressions.
fixes unnecessary_null_aware_assignments property-access false positives.
adds new lint: use_super_parameters.
adds new lint: use_enums.
adds new lint: use_colored_box.
improves performance for sort_constructors.
improves docs for always_use_package_imports, avoid_print, and avoid_relative_lib_imports .
updates avoid_void_async to skip main functions.
updates prefer_final_parameters to not super on super params.
updates lints for enhanced-enums and super-initializer language features.
updates unnecessary_late to report on variable names.
marks null_check_on_nullable_type_parameter stable.

Dartdoc

Updated dartdoc to 5.1.0, which includes changes that

support the enhanced enums feature
remove superfluous [...] links
fix categoryOrder option
display categorized extensions
add annotations to extensions
make minor improvements to performance

2.16.2 - 2022-03-24

This is a patch release that fixes a dart2js crash when building some Flutter web apps (issue #47916).

2.16.1 - 2022-02-09

This is a patch release that fixes an AOT precompiler crash when building some Flutter apps (issue flutter/flutter#97301).

2.16.0 - 2022-02-03

Core libraries

`dart:core`

Add Error.throwWithStackTrace which can throw an error with an existing stack trace, instead of creating a new stack trace.

`dart:ffi`

Add Abi and AbiSpecificInteger. These enable specifying integers which have different sizes/signs per ABI (hardware and OS combination).

`dart:io`

Security advisory CVE-2022-0451, breaking change #45410: HttpClient no longer transmits some headers (i.e. authorization, www-authenticate, cookie, cookie2) when processing redirects to a different domain.
Breaking change #47653: On Windows, Directory.rename will no longer delete a directory if newPath specifies one. Instead, a FileSystemException will be thrown.
Breaking change #47769: The Platform.packageRoot API has been removed. It had been marked deprecated in 2018, as it doesn't work with any Dart 2.x release.
Add optional sourcePort parameter to Socket.connect, Socket.startConnect, RawSocket.connect and RawSocket.startConnect

`dart:isolate`

Breaking change #47769: The Isolate.packageRoot API has been removed. It had been marked deprecated in 2018, as it doesn't work with any Dart 2.x release.

Tools

Dart command line

Breaking change #46100: The standalone dartanalyzer tool has been marked deprecated as previously announced. Its replacement is the dart analyze command. Should you find any issues, or missing features, in the replacement command, kindly file an issue.

Breaking change #46100: The standalone dartdoc tool has been marked deprecated as previously announced. Its replacement is the dart doc command. Should you find any issues, or missing features, in the replacement command, kindly file an issue.

Breaking Change #46100: The deprecated standalone pub tool has been removed. Its replacement is the dart pub command. Should you find any issues, or missing features, in the replacement command, kindly file an issue.

Pub

Fixed race conditions in dart pub get, dart run and dart pub global run. It should now be safe to run these concurrently.
If (when) Pub crashes it will save a verbose log in $PUB_CACHE/log/pub_log.txt This can be used for filing issues to the issue tracker.

dart --verbose pub [command] will also cause the log file to be written.
dart pub global activate --source=git now takes arguments --git-path to specify the path of the activated package in the pubspec and --git-ref to specify the branch or revision to check out.
dart pub add can now add multiple packages in one command.
dart pub token add can now add a token for pub.dev.
dart pub uploader has been removed. To manage uploaders for a package use the https://pub.dev/<packagename>/admin web-interface.
Pub now supports a separate pubspec_overrides.yaml file that can contain dependency_overrides. This makes it easier to avoid checking the local overrides into version control.

Linter

Updated the Linter to 1.18.0, which includes changes that

extends camel_case_types to cover enums.
fixes no_leading_underscores_for_local_identifiers to not mis-flag field formal parameters with default values.
fixes prefer_function_declarations_over_variables to not mis-flag non-final fields.
improves performance for prefer_contains.
updates exhaustive_cases to skip deprecated values that redirect to other values.
adds new lint: unnecessary_late.
improves docs for prefer_initializing_formals.
updates secure_pubspec_urls to check issue_tracker and repository entries.
adds new lint: conditional_uri_does_not_exist.
improves performance for missing_whitespace_between_adjacent_strings.
adds new lint: avoid_final_parameters.
adds new lint: no_leading_underscores_for_library_prefixes.
adds new lint: no_leading_underscores_for_local_identifiers.
adds new lint: secure_pubspec_urls.
adds new lint: sized_box_shrink_expand.
adds new lint: use_decorated_box.
improves docs for omit_local_variable_types.

2.15.1 - 2021-12-14

This is a patch release that fixes:

an AOT compilation failure in some Flutter apps (issue #47878).
dart pub publish for servers with a path in the URL (pr dart-lang/pub#3244).

2.15.0 - 2021-12-08

Security advisory CVE-2021-22567: Bidirectional Unicode text can be interpreted and compiled differently than how it appears in editors and code-review tools. Exploiting this an attacker could embed source that is invisible to a code reviewer but that modifies the behavior of a program in unexpected ways. Dart 2.15.0 introduces new analysis warnings that flags the use of these.
Security advisory CVE-2021-22568: A malicious third-party package repository may impersonate a user on pub.dev for up to one hour after the user has published a package to that third-party package repository using dart pub publish. As of Dart SDK version 2.15.0 requests to third-party package repositories will no longer include an OAuth2 access_token intended for pub.dev.

Language

The following features are new in the Dart 2.15 language version. To use them, you must set the lower bound on the SDK constraint for your package to 2.15 or greater (sdk: '>=2.15.0 <3.0.0').

Constructor tear-offs: Previous Dart versions allowed a method on an instance to be passed as a closure, and similarly for static methods. This is commonly referred to as "closurizing" or "tearing off" a method. Constructors were not previously eligible for closurization, forcing users to explicitly write wrapper functions when using constructors as first class functions. See the calls to map() in this example:
```
class A {
  int x;
  A(this.x);
  A.fromString(String s) : x = int.parse(s);
}

void main() {
  var listOfInts = [1, 2, 3];
  var listOfStrings = ["1", "2", "3"];
  for(var a in listOfInts.map((x) => A(x))) {
    print(a.x);
  }
  for(var a in listOfStrings.map((x) => A.fromString(x))) {
    print(a.x);
  }
}
```
New in Dart 2.15, constructors are now allowed to be torn off. Named constructors are closurized using their declared name (here A.fromString). To closurize unnamed constructors, use the keyword new (here A.new). The above example may now be written as:
```
class A {
  int x;
  A(this.x);
  A.fromString(String s) : x = int.parse(s);
}

void main() {
  var listOfInts = [1, 2, 3];
  var listOfStrings = ["1", "2", "3"];
  for(A a in listOfInts.map(A.new)) {
    print(a.x);
  }
  for(A a in listOfStrings.map(A.fromString)) {
    print(a.x);
  }
}
```
Constructors for generic classes may be torn off as generic functions, or instantiated at the tear-off site. In the following example, the tear-off G.new is used to initialize the variable f produces a generic function which may be used to produce an instance of G<T> for any type T provided when f is called. The tear-off G<String>.new is used to initialize the variable g to produce a non-generic function which may only be used to produce instances of type G<String>.
```
class G<T> {
  T x;
  G(this.x);
}

void main() {
  G<T> Function<T>(T x) f = G.new;
  var x = f<int>(3);
  G<String> Function(String y) g = G<String>.new;
  var y = g("hello");
}
```

Generic type literals: Previous Dart versions allowed class names to be used as type literals. So for example,int may be used as an expression, producing a value of type Type. Generic classes (e.g. List) could be referred to by name as an expression, but no type arguments could be provided and so only the dynamic instantiation could be produced directly as an expression without using indirect methods:

// Workaround to capture generic type literals.
Type typeOf<T>() => T;

void main() {
  var x = int; // The Type literal corresponding to `int`.
  var y = List; // The Type literal corresponding to `List<dynamic>`.
  // Use workaround to capture generic type literal.
  var z = typeOf<List<int>>(); // The Type literal for `List<int>`.
}

New in Dart 2.15, instantiations of generic classes may now be used as Type literals:

void main() {
  var x = int; // The Type literal corresponding to `int`.
  var y = List; // The Type literal corresponding to `List<dynamic>`.
  var z = List<int>; // The Type literal corresponding to `List<int>`.
}

Explicit generic method instantiations: Previous Dart versions allowed generic methods to be implicitly specialized (or "instantiated") to non-generic versions when assigned to a location with a compatible monomorphic type. Example:

// The generic identity function.
T id<T>(T x) => x;

void main() {
  // Initialize `intId` with a version of `id` implicitly specialized to
  // `int`.
  int Function(int) intId = id;
  print(intId(3));
  // Initialize `stringId` with a version of `id` implicitly specialized to
  // `String`.
  String Function(String) stringId = id;
  print(stringId("hello"));
}

New in Dart 2.15, generic methods may be explicitly instantiated using the syntax f<T> where f is the generic method to specialize and T is the type argument (in general, type arguments) to be used to specialize the method. Example:

// The generic identity function.
T id<T>(T x) => x;

void main() {
  // Initialize `intId` with a version of `id` explicitly specialized to
  // `int`.
  var intId = id<int>;
  print(intId(3));
  // Initialize `stringId` with a version of `id` explicitly specialized to
  // `String`.
  var stringId = id<String>;
  print(stringId("hello"));
}

Generic instantiation of function objects: Generic function instantiation was previously restricted to function declarations. For example, as soon as a function had been torn off, it could not be instantiated:

// Before Dart 2.15:
X id<X>(X x) => x;

void main() {
  var fo = id; // Tear off `id`, creating a function object.
  var c1 = fo<int>; // Compile-time error: can't instantiate `fo`.
  int Function(int) c2 = fo; // Same compile-time error.
  // Constants are treated the same.
}

New in Dart 2.15, this restriction has been lifted. It is now possible to obtain a generic instantiation of an existing function object, both explicitly and implicitly (again, this works the same for non-constants):

X id<X>(X x) => x;
X other<X>(X x) => throw x;

void main() {
  const fo = id; // Tear off `id`, creating a function object.

  // Generic function instantiation on `fo` is no longer an error.
  const c1 = fo<int>; // OK.
  const int Function(int) c2 = fo; // OK.

  // This also generalizes function instantiation because we can,
  // e.g., use non-trivial expressions and go via a constructor.
  const c3 = A(true); // OK.
}

class A {
  final int Function(int) x;
  // `(...)<T>` is now allowed, also in a `const` constructor.
  const A(bool b): x = (b ? id : other)<int>;
}

Annotations on type parameters of classes can no longer refer to class members without a prefix. For example, this used to be permitted:
```
class C<@Annotation(foo) T> {
  static void foo() {}
}
```
Now, the reference must be qualified with the class name, i.e.:
```
class C<@Annotation(C.foo) T> {
  static void foo() {}
}
```
This brings the implementation behavior in line with the spec.
Initializer expressions on implicitly typed condition variables can now contribute to type promotion. For example, this program no longer produces a compile-time error:
```
f(int? i) {
  var iIsNull = i == null;
  if (!iIsNull) {
    print(i + 1); // OK, because `i` is known to be non-null.
  }
}
```
Previously, the above program had a compile-time error due to a bug (#1785) in type promotion which prevented the initializer expression (i == null) from being accounted for when the variable in question (iIsNull) lacked an explicit type.

To avoid causing problems for packages that are intended to work with older versions of Dart, the fix only takes effect when the minimum SDK of the source packages is 2.15 or greater.

Restrictions on members of a class with a constant constructor are relaxed such that they only apply when the class has a generative constant constructor. For example, this used to be an error, but is now permitted:
```
abstract class A {
  const factory A() = B;
  var v1;
  late final v2 = Random().nextInt(10);
  late final v3;
}

class B implements A {
  const B([this.v3 = 1]);
  get v1 => null;
  set v1(_) => throw 'Cannot mutate B.v1';
  final v2 = 0;
  final v3;
  set v3(_) => throw 'Cannot initialize B.v3';
}
```
This implements a relaxation of the specified rule for a late final instance variable, and it brings the implementation behavior in line with the specification in all other cases.
Function object canonicalization and equality: Several corner cases in the area of function object canonicalization and function object equality have been updated, such that all tools behave in the same way, and the behavior matches the specification.

In particular, function objects are now equal when they are obtained by generic instantiation from the same function with the same actual type arguments, even when that type argument is not known at compile time. When the expressions are constant then the function objects are identical. Constant expressions are treated as such even when they do not occur in a constant context (e.g., var f = top;).

Core libraries

`dart:async`

Make the unawaited function's argument nullable, to allow calls like unawaited(foo?.bar()).

`dart:cli`

The experimental waitFor functionality, and the library containing only that function, are now deprecated.

`dart:core`

Add extension name getter on enum values.
Add Enum.compareByIndex helper function for comparing enum values by index.
Add Enum.compareByName helper function for comparing enum values by name.
Add extension methods on Iterable<T extends Enum>, intended for SomeEnumType.values lists, to look up values by name.
Deprecate IntegerDivisionByZeroException. Makes the class also implement Error. Code throwing the exception will be migrated to throwing an Error instead until the class is unused and ready to be removed. Code catching the class should move to catching Error instead (or, for integers, check first for whether it's dividing by zero).

`dart:ffi`

Add Bool native type.

`dart:io`

Breaking change #46875: The SecurityContext class in dart:io has been updated to set the minimum TLS protocol version to TLS1_2_VERSION (1.2) instead of TLS1_VERSION.
Add RawSocket.sendMessage, RawSocket.receiveMessage that allow passing of file handle references via Unix domain sockets.

`dart:js_util`

The js_util methods setProperty, callMethod, and callConstructor have been optimized to remove checks on arguments when the checks can be elided. Also, those methods, along with getProperty and newObject, now support a generic type argument to specify a return type. These two changes make simple js_util usage, like reading and writing primitive properties or calling methods with simple arguments, have zero overhead.

`dart:web_sql`

Breaking change #46316: The WebSQL standard was abandoned more than 10 years ago and is not supported by many browsers. This release completely deletes the dart:web_sql library.

`dart:html`

Breaking change #46316: Related to the removal of dart:web_sql (see above), window.openDatabase has been removed.

Tools

Dart command line

Breaking change #46100: The standalone dart2native tool has been removed as previously announced. Its replacements are the dart compile exe and dart compile aot-snapshot commands, which offer the same functionality.
Breaking change: The standalone dartfmt tool has been removed as previously announced. Its replacement is the dart format command.

Note that dart format has a different set of options and defaults than dartfmt.
When a script is dart run it will always be precompiled, but with incremental precompilation for following runs.

Dart VM

Breaking change #45451: Support for dart-ext:-style native extensions has been removed as previously announced. Use dart:ffi to bind to native libraries instead.
Breaking change #46754: Isolates spawned via the Isolate.spawn() API are now grouped, operate on the same managed heap and can therefore share various VM-internal data structures.

This leads to ~100x faster isolate startup latency, ~10-100x lower per-isolate base memory overhead and ~8x faster inter-isolate communication.

Making isolates operate on the same heap will also make them collaborate on garbage collections, which changes performance characteristics for GC-heavy applications that may - in rare cases - negatively affect pause times or throughput.
Allow closures both in inter-isolate messages as well as as entrypoints in Isolate.spawn(<entrypoint>, ...) calls. Closures and their enclosing context may need to be copied in this process. The enclosing context is - as with normal messages - verified to only contain objects that are sendable.

Note of caution: The Dart VM's current representation of enclosing variables in closures can make closures hang on to more variables than strictly needed. Using such closures in inter-isolate communication can therefore lead to copying of larger transitive object graphs. If the extended transitive closure includes objects that are illegal to send, the sending will fail. See #36983, which tracks this existing memory leak issue.

Linter

Updated the Linter to 1.14.0, which includes changes that

improves performance for annotate_overrides, prefer_contains, and prefer_void_to_null.
marks avoid_dynamic_calls stable.
fixed avoid_null_checks_in_equality_operators false positive with non-nullable params.
update avoid_print to allow kDebugMode-wrapped print calls.
adds support for constructor tear-offs to avoid_redundant_argument_values, unnecessary_lambdas, and unnecessary_parenthesis.
improves messages for avoid_renaming_method_parameters.
improves regular expression parsing performance for common checks (camel_case_types, file_names, etc.).
fixed file_names to report at the start of the file (not the entire compilation unit).
allow while (true) { ... } in literal_only_boolean_expressions.
fixed omit_local_variable_types false positives.
fixed omit_local_variable_types to not flag a local type that is required for inference.
fixed overridden_fields false positive with static fields.
fixed prefer_collection_literals named typed parameter false positives.
fixed prefer_const_constructors false positive for deferred imports.
fixed prefer_final_parameters handling of initializing formals.
fixed prefer_generic_function_type_aliases false positives with incomplete statements.
fixed prefer_initializing_formals false positives with factory constructors.
fixed prefer_void_to_null false positive with overridden properties.
fixed prefer_void_to_null false positives on overriding returns.
fixed prefer_void_to_null false positives.
adds a new lint: unnecessary_constructor_name to flag unnecessary uses of .new.
updates unnecessary_getters_setters to only flag the getter.
fixed unnecessary_parenthesis false positive with function expressions.
fixed use_build_context_synchronously false positive in awaits inside anonymous functions.
improve control flow analysis for use_build_context_synchronously.
fixed use_rethrow_when_possible false positives.
fixed void_checks false positives with incomplete source.

Pub

If you have analytics enabled dart pub get will send usage metrics for packages from pub.dev, intended for popularity analysis.
Adds support for token-based authorization to third-party package-repositories with the new command dart pub token.
Credentials are no longer stored in the pub-cache, but in a platform dependent config directory:
- On Linux $XDG_CONFIG_HOME/dart/pub-credentials.json if $XDG_CONFIG_HOME is defined, otherwise $HOME/.config/dart/pub-credentials.json
- On Mac OS: $HOME/Library/Application Support/dart/pub-credentials.json
- On Windows: %APPDATA%/dart/pub-credentials.json
The syntax for dependencies hosted at a third-party package repository has been simplified. Before you would need to write:

dependencies:
  colorizer:
    hosted:
      name: colorizer
      url: 'https://custom-pub-server.com'
    version: ^1.2.3
environment:
  sdk: '>=2.14.0 < 3.0.0'

Now you can write:

dependencies:
  colorizer:
    hosted: 'https://custom-pub-server.com'
    version: ^1.2.3
environment:
  sdk: '>=2.15.0 < 3.0.0'

This feature requires language version 2.15 or later, e.g. the pubspec.yaml should have an SDK constraint of >=2.15 <3.0.0.

Detect potential leaks in dart pub publish. When publishing, pub will examine your files for potential secret keys, and warn you.

To ignore a file that has a false positive, add it to a false_secrets section of your pubspec.yaml.
Fixes unicode terminal detection windows.
New flag --example to the commands dart pub get/upgrade/downgrade/add/remove that will result in the example/ folder dependencies to be updated after operating in the current directory.

Other libraries

`package:js`

Extensions on JS interop or native dart:html classes can now declare members as external. These members are equivalent to regular extension members that use js_util to expose the underlying JavaScript.

2.14.4 - 2021-10-14

This is a patch release that fixes:

a memory leak of analyzer plugins (issue flutter/flutter#90868).
the Dart VM sometimes loading expired certificates on Windows (issues #46370 and #47420).

2.14.3 - 2021-09-30

This is a patch release that fixes:

a code completion performance regression (issue flutter/flutter-intellij#5761).
debug information emitted by the Dart VM (issue #47289).

2.14.2 - 2021-09-16

This is a patch release that fixes:

two dartdoc crashes (issues dart-lang/dartdoc#2740 and dart-lang/dartdoc#2755).
error messages when using the >>> operator on older language versions (issue #46886).
invalid pubspec.lock paths on Windows (issue dart-lang/pub#3012).

2.14.1 - 2021-09-09

Fixed an issue specific to the macOS ARM64 (Apple Silicon) SDK, where the Dart commandline tools did not have the expected startup performance.

2.14.0 - 2021-09-09

Language

Add an unsigned shift right operator >>>. Pad with zeroes, ignoring the sign bit. On the web platform int.>>> shifts the low 32 bits interpreted as an unsigned integer, so a >>> b gives the same result as a.toUnsigned(32) >>> b on the VM.
Prior to Dart 2.14, metadata (annotations) were not permitted to be specified with generic type arguments. This restriction is lifted in Dart 2.14.
```
class C<T> {
  const C();
}
@C();      // Previously permitted.
@C<int>(); // Previously an error, now permitted.
```

Prior to Dart 2.14, generic function types were not permitted as arguments to generic classes or functions, nor to be used as generic bounds. This restriction is lifted in Dart 2.14.

T wrapWithLogging<T>(T f) {
  if (f is void Function<T>(T x)) {
    return <S>(S x) {
      print("Call: f<$S>($x)");
      var r = f<S>(x);
      print("Return: $x");
      return r;
    } as T;
  } // More cases here
  return f;
}
void foo<T>(T x) {
  print("Foo!");
}
void main() {
  // Previously an error, now permitted.
  var f = wrapWithLogging<void Function<T>(T)>(foo);
  f<int>(3);
}

Core libraries

`dart:async`

The uncaught error handlers of Zones are now run in the parent zone of the zone where they were declared. This prevents a throwing handler from causing an infinite loop by repeatedly triggering itself.
Added ignore() as extension member on futures.
Added void unawaited(Future) top-level function to deal with the unawaited_futures lint.

`dart:core`

Introduce Enum interface implemented by all enum declarations.
The native DateTime class now better handles local time around daylight saving changes that are not precisely one hour. (No change on the Web which uses the JavaScript Date object.)
Adds static methods hash, hashAll and hashAllUnordered to the Object class. These can be used to combine the hash codes of multiple objects in a consistent way.
The Symbol constructor now accepts any string as argument. Symbols are equal if they were created from the same string.

`dart:ffi`

Add the DynamicLibrary.providesSymbol function to check whether a symbol is available in a dynamic library.
Add Union native type for interacting with unions in native memory.

`dart:html`

convertNativeToDart_Dictionary() now converts objects recursively, this fixes APIs like MediaStreamTrack.getCapabilities that convert between Maps and browser Dictionaries. #44319
Added some access-control HTTP header names to HttpHeaders.

`dart:io`

BREAKING CHANGE (for pre-migrated null safe code): HttpClient's .authenticate and .authenticateProxy setter callbacks must now accept a nullable realm argument.
Added some access-control HTTP header names to HttpHeaders.

`dart:typed_data`

BREAKING CHANGE (#45115) Most types exposed by this library can no longer be extended, implemented or mixed-in. The affected types are ByteBuffer, TypedData and all its subclasses, Int32x4, Float32x4, Float64x2 and Endian.

`dart:web_sql`

dart:web_sql is marked deprecated and will be removed in an upcoming release. Also the API window.openDatabase in dart:html is deprecated as well.

This API and library was exposing the WebSQL proposed standard. The standard was abandoned more than 5 years ago and is not supported by most browsers. The dart:web_sql library has been documented as unsupported and deprecated for many years as well and but wasn't annotated properly until now.

Dart VM

Breaking change #45071: Dart_NewWeakPersistentHandle's and Dart_NewFinalizableHandle's object parameter no longer accepts Pointers and subtypes of Struct. Expandos no longer accept Pointers and subtypes of Structs.

Tools

Dart command line

Breaking change #46100: The standalone dart2native tool has been marked deprecated, and now prints a warning message. Its replacements are the dart compile exe and dart compile aot-snapshot commands, which offer the same functionality. The dart2native tool will be removed from the Dart SDK in Dart 2.15.
Breaking change: The standalone dartfmt tool has been marked deprecated, and now prints a warning message. Instead, use dart format. The dartfmt tool will be removed from the Dart SDK in Dart 2.15.

Note that dart format has a different set of options and defaults than dartfmt.
The dart create command has been updated to create projects that use the new 'recommended' set of lints from package:lints. See https://dart.dev/go/core-lints for more information about these lints.

The dart analyze command has been extended to support specifying multiple files or directories to analyze; see also #45352.
The dartanalyzer command's JSON output mode has been changed to emit the JSON output on stdout instead of stderr.

dart format

Simplify and optimize cascade formatting. See: dart-lang/dart_style#1033
Don't unnecessarily split argument lists with /* */ comments.
Return correct exit code from FormatCommand when formatting stdin.
Split empty catch blocks with finally clauses or catches after them.

Linter

Updated the Linter to 1.8.0, which includes changes that

improve performance for prefer_is_not_empty.
fix false positives in no_logic_in_create_state.
improve package_names to allow dart identifiers as package names.
fix a false-positive in package_names (causing keywords to wrongly get flagged).
fix avoid_classes_with_only_static_member to check for inherited members and also flag classes with only methods.
fix curly_braces_in_flow_control_structures to properly flag terminating else-if blocks.
improve always_specify_types to support type aliases.
fix a false positive in unnecessary_string_interpolations w/ nullable interpolated strings
fix a false positive in avoid_function_literals_in_foreach_calls for nullable iterables.
fix false positives in avoid_returning_null w/ NNBD
fix false positives in use_late_for_private_fields_and_variables in the presence of const constructors.
adds a new lint: eol_at_end_of_file.
fix case-sensitive false positive in use_full_hex_values_for_flutter_colors.
improve try-block and switch statement flow analysis for use_build_context_synchronously.
update use_setters_to_change_properties to only highlight a method name, not the entire body and doc comment.
update unnecessary_getters_setters to allow otherwise "unnecessary" getters and setters with annotations.
update missing_whitespace_between_adjacent_strings to allow String interpolations at the beginning and end of String literals.
update unnecessary_getters_setters to allow for setters with non-basic assignments (for example, ??= or +=).
relax non_constant_identifier_names to allow for a trailing underscore.
fix false negative in prefer_final_parameters where first parameter is final.
improve directives_ordering sorting of directives with dot paths and dot-separated package names.
(internal) migrate to SecurityLintCode instead of deprecated SecurityLintCodeWithUniqueName.
(internal) fix avoid_types_as_parameter_names to skip field formal parameters.
fix false positives in prefer_interpolation_to_compose_strings where the left operand is not a String.
fix false positives in only_throw_errors for misidentified type variables.
add new lint: depend_on_referenced_packages.
update avoid_returning_null_for_future to skip checks for null-safe libraries.
add new lint: use_test_throws_matchers.
relax sort_child_properties_last to accept closures after child.
improve performance for prefer_contains and prefer_is_empty.
add new lint: noop_primitive_operations.
mark avoid_web_libraries_in_flutter as stable.
add new lint: prefer_final_parameters.
update prefer_initializing_formals to allow assignments where identifier names don't match.
update directives_ordering to checks ordering of package: imports in code outside pub packages.
add simple reachability analysis to use_build_context_synchronously to short-circuit await-discovery in terminating blocks.
update use_build_context_synchronously to recognize nullable types when accessed from legacy libraries.

Pub

dart pub publish now respects .pubignore files with gitignore-style rules. .gitignore files in the repo are still respected if they are not overridden by a .pubignore in the same directory.

pub no longer queries git for listing the files. This implies:
- Checked in files will now be ignored if they are included by a .gitignore rule.
- Global ignores are no longer taken into account.
- Even packages that are not in git source control will have their .gitignore files respected.
- .gitignore and .pubignore is always case-insensitive on MacOs and Windows (as is default for git repositories).
New flag dart pub deps --json gives a machine parsable overview of the current dependencies.
New command: dart pub cache clean. Will delete everything in your current pub cache.
Commands related to a single package now takes a --directory option to operate on a package in the given directory instead of the working directory.
git dependencies with a relative repo url would previously be interpreted relative to the current package, even for transitive dependencies. This now fails instead.
Pub now uses a Dart library to read and write tar files. This should fix several issues we had with incompatibilities between different system tars.
PUB_HOSTED_URL can now include a trailing slash.
Incremental compilation is now used for compilation of executables from dependencies when using dart run <package>:<command>.

Dart2JS

Breaking change #46545: Dart2JS emits ES6+ JavaScript by default, thereby no longer supporting legacy browsers. Passing the --legacy-javascript flag will let you opt out of this update, but this flag will be removed in a future release. Modern browsers will not be affected, as Dart2JS continues to support last two major releases of Edge, Safari, Firefox, and Chrome.

Dart Dev Compiler (DDC)

Breaking change #44154: Subtyping relations of package:js classes have been changed to be more correct and consistent with Dart2JS. Like anonymous classes, non-anonymous classes will no longer check the underlying type in DDC. The internal type representation of these objects have changed as well, which will affect the toString value of these types.

2.13.4 - 2021-06-28

This is a patch release that fixes:

a Dart VM compiler crash (issue flutter/flutter#84212).
a DDC compiler crash (issue flutter/flutter#82838).

2.13.3 - 2021-06-10

This is a patch release that fixes:

a Dart compiler crash (issue flutter/flutter#83094).
an analysis server deadlock causing it to stop responding to IDE requests (issue #45996).
an analyzer crash when analyzing against package:meta v1.4.0 (issue #46183).

2.13.1 - 2021-05-25

This is a patch release that fixes:

incorrect behavior in CastMap (issue #45473).
missing nullability from recursive type hierarchies in DDC (issue #45767).

2.13.0 - 2021-05-18

Language

Type aliases Non-function type aliases: Type aliases (names for types introduced via the typedef keyword) were previously restricted to only introduce names for function types. In this release, we remove this restriction and allow type aliases to name any kind of type.
```
import 'dart:convert';

typedef JsonMap = Map<String, dynamic>;

JsonMap parseJsonMap(String input) => json.decode(input) as JsonMap;
```
In addition to being usable as type annotations, type aliases that name class types can now also be used anywhere that the underlying class could be used, allowing type aliases to be used to safely rename existing classes.
```
class NewClassName<T> {
   NewClassName.create(T x);
   static NewClassName<T> mkOne<T>(T x) => NewClassName<T>.create(x);
 }
@Deprecated("Use NewClassName instead")
typedef OldClassName<T> = NewClassName<T>;

class LegacyClass extends OldClassName<int> {
  LegacyClass() : super.create(3);
}
OldClassName<int> legacyCode() {
  var one = OldClassName.create(1);
  var two = OldClassName.mkOne(2);
  return LegacyClass();
}
```
The new type alias feature is only available as part of the 2.13 language version. To use this feature, you must set the lower bound on the sdk constraint for your package to 2.13 or greater.

Core libraries

`dart:collection`

The SplayTreeMap was changed to allow null as key if the compare function allows it. It now checks that a new key can be used as an argument to the compare function when the member is added, even if the map is empty (in which case it just compares the key to itself).
The SplayTreeSet was changed to checks that a new element can be used as an argument to the compare function when the member is added, even if the set is empty (in which case it just compares the element to itself).

`dart:developer`

Added serverWebSocketUri property to ServiceProtocolInfo.

`dart:ffi`

Add Packed for interacting with packed structs in native memory.
Add Array for interacting with structs with inline arrays.

Dart VM

Tools

Analyzer

Static analyses with "error" severity can once again be ignored with comments like // ignore: code and // ignore_for_file: code. To declare that certain analysis codes, or codes with certain severities ("error", "warning", and "info") cannot be ignored with such comments, list them in analysis_options.yaml, under the analyzer heading, with a new YAML key, cannot-ignore. For example, to declare that "error" codes and unused_import cannot be ignored, write the following into analysis_options.yaml:
```
analyzer:
  cannot-ignore:
    - error
    - unused_import
```

dart format

Correct constructor initializer indentation after required named parameters.

Linter

Updated the Linter to 1.2.1, which includes:

Improved iterable_contains_unrelated_type to better support List content checks.
Fixed camel_case_types and prefer_mixin to support non-function type aliases.
Fixed prefer_mixin to properly make exceptions for dart.collection legacy mixins.
Added new lints avoid_multiple_declarations_per_line, use_if_null_to_convert_nulls_to_bools, deprecated_consistency, use_named_constants, use_build_context_synchronously (experimental).
Deprecated avoid_as.
Migrated library to null-safety.

Other libraries

`package:js`

Breaking change: It is no longer valid to use Strings that match an @Native annotation in an @JS() annotation for a non-anonymous JS interop class. This led to erroneous behavior due to the way interceptors work. If you need to work with a native class, prefer dart:html, an @anonymous class, or js_util. See issue #44211 for more details.

2.12.4 - 2021-04-15

This is a patch release that fixes a Dart VM compiler crashes when compiling initializers containing async closures (issue #45306).

2.12.3 - 2021-04-14

Security advisory: This is a patch release that fixes a vulnerability in dart:html related to DOM clobbering. See the security advisory CVE-2021-22540 for more details. Thanks again to Vincenzo di Cicco for finding and reporting this vulnerability.

2.12.2 - 2021-03-17

This is a patch release that fixes crashes reported by Flutter 2 users (issue flutter/flutter#78167).

2.12.1 - 2021-03-10

This is a patch release that fixes:

an unhandled exception in HTTPS connections (issue #45047).
a typing issue in the typed_data + operator (issue #45140).

2.12.0 - 2021-03-03

Language

Breaking change Null safety is now enabled by default in all code that has not opted out. With null safety, types in your code are non-nullable by default. Null can only flow into parts of your program where you want it. With null safety, your runtime null-dereference bugs turn into edit-time analysis errors.

You can opt out of null safety and preserve your code's previous behavior by setting the lower bound of the SDK constraint in your pubspec to 2.11.0 or earlier to request an earlier language version. You can opt out individual Dart files by adding // @dart=2.11 to the beginning of the file.

Files that are opted in to null safety may report new compile-time errors. Opting in to null safety also gives you access to other new language features:
- Smarter flow analysis and type promotion
- required named parameters
- late variables
- The postfix ! null assertion operator
- The ?.. and ?[] null-aware operators
Breaking change #44660: Fixed an implementation bug where this would sometimes undergo type promotion in extensions.

Core libraries

`dart:async`

Add extension method onError() on Future to allow better typing of error callbacks.

`dart:collection`

Add UnmodifiableSetView class, which allows users to guarantee that methods that could change underlying Set instance can not be invoked.
Make it explicit that LinkedList compares elements by identity, and update contains() to take advantage of this.

`dart:core`

Add Set.unmodifiable() constructor, which allows users to create unmodifiable Set instances.

`dart:ffi`

Breaking change #44621: Invocations with a generic T of sizeOf<T>, Pointer<T>.elementAt(), Pointer<T extends Struct>.ref, and Pointer<T extends Struct>[] are being deprecated in the current stable release (2.12), and are planned to be fully removed in the following stable release (2.13). Consequently, allocate in package:ffi will no longer be able to invoke sizeOf<T> generically, and will be deprecated as well. Instead, the Allocator it is introduced to dart:ffi, and also requires a constant T on invocations. For migration notes see the breaking change request.
Breaking change #44622: Subtypes of Struct without any native member are being deprecated in the current stable release (2.12), and are planned to be fully removed in the following stable release (2.13). Migrate opaque types to extend Opaque rather than Struct.

`dart:io`

HttpRequest now correctly follows HTTP 308 redirects (HttpStatus.permanentRedirect).

`dart:isolate`

Add debugName positional parameter to ReceivePort and RawReceivePort constructors, a name which can be associated with the port and displayed in tooling.
Introduce Isolate.exit([port, message]) which terminates current isolate and, if port is specified, as a last action sends out the message out to that port.

`dart:html`

EventStreamSubscription.cancel has been updated to retain its synchronous timing when running in both sound and unsound null safety modes. See issue #44157 for more details.

Dart VM

Breaking change #42312: Dart_WeakPersistentHandles no longer auto-delete themselves when the referenced object is garbage collected to avoid race conditions, but they are still automatically deleted when the isolate group shuts down.
Breaking change #42312: Dart_WeakPersistentHandleFinalizer is renamed to Dart_HandleFinalizer and had its handle argument removed. All API functions using that type have been updated.

Dart2JS

Remove --no-defer-class-types and --no-new-deferred-split.

Tools

Analyzer

Remove the --use-fasta-parser, --preview-dart-2, and --enable-assert-initializers command line options. These options haven't been supported in a while and were no-ops.
Report diagnostics regarding the @internal annotation.
Improve diagnostic-reporting regarding the @doNotStore annotation.
Introduce a diagnostic which is reported when a library member named main is not a function.
Introduce a diagnostic which is reported when a main function's first parameter is not a supertype of List<String>.
Introduce diagnostics for when an // ignore comment contains an error code which is not being reported, cannot be ignored, or is already being ignored.
Report diagnostics when using [@visibleForTesting](https://pub.dev/documentation/meta/latest/meta/ visibleForTesting-constant.html) on top-level variables.
Fix false positive reports of "unused element" for top-level setters and getters.
Fix false positive reports regarding @deprecated field formal parameters at their declaration.
For null safety, introduce a diagnostic which reports when a null-check will always fail.
Fix false positive reports regarding optional parameters on private constructors being unused.
Introduce a diagnostic which is reported when a constructor includes duplicate field formal parameters.
Improve the "unused import" diagnostic when multiple import directives share a common prefix.
Fix false positive "unused import" diagnostic regarding an import which provides an extension method which is used.
For null safety, improve the messaging of "use of nullable value" diagnostics for eight different contexts.
Fix false positive reports regarding @visibleForTesting members in a "hide" combinator of an import or export directive.
Improve the messaging of "invalid override" diagnostics.
Introduce a diagnostic which is reported when Future<T>.catchError is called with an onError callback which does not return FutureOr<T>.

dartfmt

Don't duplicate comments on chained if elements.
Preserve ? in initializing formal function-typed parameters.
Fix performance issue with constructors that have no initializer list.

Linter

Updated the Linter to 0.1.129, which includes:

New lints: avoid_dynamic_calls, cast_nullable_to_non_nullable, null_check_on_nullable_type_parameter, tighten_type_of_initializing_formals, unnecessary_null_checks, and avoid_type_to_string.
Fix crash in prefer_collection_literals when there is no static parameter element.
Fix false negatives for prefer_collection_literals when a LinkedHashSet or LinkedHashMap instantiation is passed as the argument to a function in any position other than the first.
Fix false negatives for prefer_collection_literals when a LinkedHashSet or LinkedHashMap instantiation is used in a place with a static type other than Set or Map.
Update to package_names to allow leading underscores.
Fix crashes in unnecessary_null_checks and missing_whitespace_between_adjacent_strings.
Update to void_checks for null safety.
Fix range error in unnecessary_string_escapes.
Fix false positives in unnecessary_null_types.
Fix to prefer_constructors_over_static_methods to respect type parameters.
Update to always_require_non_null_named_parameters to be null safety-aware.
Update to unnecessary_nullable_for_final_variable_declarations to allow dynamic.
Update overridden_fields to not report on abstract parent fields.
Fix to unrelated_type_equality_checks for null safety.
Improvements to type_init_formalsto allow types not equal to the field type.
Updates to public_member_apis to check generic type aliases.
Fix close_sinks to handle this-prefixed property accesses.
Fix unawaited_futures to handle Future subtypes.
Performance improvements to always_use_package_imports, avoid_renaming_method_parameters, prefer_relative_imports and public_member_api_docs.

Pub

Breaking: The Dart SDK constraint is now required in pubspec.yaml. You must include a section like:
```
environment:
  sdk: ">=2.10.0 <3.0.0"
```
See #44072.

For legacy dependencies without an SDK constraint, pub will now assume a default language version of 2.7.
The top level pub executable has been deprecated. Use dart pub instead. See dart tool.
New command dart pub add that adds new dependencies to your pubspec.yaml, and a corresponding dart pub remove that removes dependencies.
New option dart pub upgrade --major-versions will update constraints in your pubspec.yaml to match the resolvable column reported in dart pub outdated. This allows users to easily upgrade to latest version for all dependencies where this is possible, even if such upgrade requires an update to the version constraint in pubspec.yaml.

It is also possible to only upgrade the major version for a subset of your dependencies using dart pub upgrade --major-versions <dependencies...>.
New option dart pub upgrade --null-safety will attempt to update constraints in your pubspec.yaml, such that only null-safety migrated versions of dependencies are allowed.
New option dart pub outdated --mode=null-safety that will analyze your dependencies for null-safety.
dart pub get and dart pub upgrade will highlight dependencies that have been discontinued on pub.dev.
dart pub publish will now check your pubspec keys for likely typos.
dart pub upgrade package_foo fetches dependencies but ignores the pubspec.lock for package_foo, allowing users to only upgrade a subset of dependencies.
New command dart pub login that logs into pub.dev.
The --server option to dart pub publish and dart pub uploader are deprecated. Use publish_to in your pubspec.yaml or set the $PUB_HOSTED_URL environment variable.
pub global activate no longer re-precompiles if the current global installation was same version.
The Flutter SDK constraint upper bound is now ignored in pubspecs and deprecated when publishing. See: flutter-upper-bound-deprecation.

2.10.5 - 2021-01-21

This is a patch release that fixes a crash in the Dart VM. (issue #44563).

2.10.4 - 2020-11-12

This is a patch release that fixes a crash in the Dart VM (issues #43941, flutter/flutter#43620, and Dart-Code/Dart-Code#2814).

2.10.3 - 2020-10-29

This is a patch release that fixes the following issues:

breaking changes in Chrome 86 that affect DDC (issues #43750 and #43193).
compiler error causing incorrect use of positional parameters when named parameters should be used instead (issues flutter/flutter#65324 and flutter/flutter#68092).
crashes and/or undefined behavior in AOT compiled code (issues #43770 and #43786).
AOT compilation of classes with more than 64 unboxed fields (issue flutter/flutter#67803).

2.10.2 - 2020-10-15

This is a patch release that fixes a DDC compiler crash (issue #43589).

2.10.1 - 2020-10-06

This is a patch release that fixes the following issues:

crashes when developing Flutter applications (issue #43464).
non-deterministic incorrect program behaviour and/or crashes (issue flutter/flutter#66672).
uncaught TypeErrors in DDC (issue #43661).

2.10.0 - 2020-09-28

Core libraries

`dart:io`

Adds Abort method to class HttpClientRequest, which allows users to cancel outgoing HTTP requests and stop following IO operations.
A validation check is added to path of class Cookie. Having characters ranging from 0x00 to 0x1f and 0x3b (";") will lead to a FormatException.
The HttpClient and HttpServer classes now have a 1 MiB limit for the total size of the HTTP headers when parsing a request or response, instead of the former 8 KiB limit for each header name and value. This limit cannot be configured at this time.

`dart:typed_data`

Class BytesBuilder is moved from dart:io to dart:typed_data. It's temporarily being exported from dart:io as well.

`dart:uri`

[#42564]: Solved inconsistency in Uri.https and Uri.http constructors' queryParams type.

Dart VM

Breaking change #42982: dart_api_dl.cc is renamed to dart_api_dl.c and changed to a pure C file.
Introduces Dart_FinalizableHandles. They do auto-delete, and the weakly referred object cannot be accessed through them.

Dart2JS

Adds support for deferred loading of types separately from classes. This enables dart2js to make better optimization choices when deferred loading. This work is necessary to address unsoundness in the deferred loading algorithm. Currently, fixing this unsoundness would result in code bloat, but loading types separately from classes will allow us to fix the unsoundness with only a minimal regression. To explicitly disable deferred loading of types, pass --no-defer-class-types. See the original post on the unsoundness in the deferred loading algorithm.
Enables a new sound deferred splitting algorithm. To explicitly disable the new deferred splitting algorithm, pass --no-new-deferred-split. See the original post on the unsoundness in the deferred loading algorithm.

Tools

dartfmt

Don't crash when non-ASCII whitespace is trimmed.
Split all conditional expressions (?:) when they are nested.
Handle external and abstract fields and variables.

Linter

Updated the Linter to 0.1.118, which includes:

New lint: unnecessary_nullable_for_final_variable_declarations.
Fixed NPE in prefer_asserts_in_initializer_lists.
Fixed range error in unnecessary_string_escapes.
unsafe_html updated to support unique error codes.
Updates to diagnostic_describe_all_properties to check for Diagnosticables (not DiagnosticableMixins).
New lint: use_late.
Fixed unnecessary_lambdas to respect deferred imports.
Updated public_member_api_docs to check mixins.
Updated unnecessary_statements to skip as expressions.
Fixed prefer_relative_imports to work with path dependencies.

Pub

pub run and pub global run accepts a --(no-)-sound-null-safety flag, that is passed to the VM.
Fix: Avoid multiple recompilation of binaries in global packages.
Fix: Avoid exponential behaviour of error reporting from the solver.
Fix: Refresh binstubs after recompile in global run.

2.9.3 - 2020-09-08

This is a patch release that fixes DDC to handle a breaking change in Chrome (issue #43193).

2.9.2 - 2020-08-26

This is a patch release that fixes transient StackOverflow exceptions when building Flutter applications (issue flutter/flutter#63560).

2.9.1 - 2020-08-12

This is a patch release that fixes unhandled exceptions in some Flutter applications (issue flutter/flutter#63038).

2.9.0 - 2020-08-05

Language

Core libraries

`dart:async`

Adds Stream.multi constructor creating streams which can be listened to more than once, and where each individual listener can be controlled independently.

`dart:convert`

Breaking change #41100: When encoding a string containing unpaired surrogates as UTF-8, the unpaired surrogates will be encoded as replacement characters (U+FFFD). When decoding UTF-8, encoded surrogates will be treated as malformed input. When decoding UTF-8 with allowMalformed: true, the number of replacement characters emitted for malformed input sequences has been changed to match the WHATWG encoding standard.

`dart:io`

#42006: The signature of exit has been changed to return the Nevertype instead of void. since no code will run after it,
Class OSError now implements Exception. This change means OSError will now be caught in catch clauses catching Exceptions.
Added InternetAddress.tryParse.
Abstract Unix Domain Socket is supported on Linux/Android now. Using an InternetAddress with address starting with '@' and type being InternetAddressType.Unix will create an abstract Unix Domain Socket.
On Windows, file APIs can now handle files and directories identified by long paths (greater than 260 characters). It complies with all restrictions from Long Path on Windows. Note that Directory.current does not work with long path.

`dart:html`

Breaking change: CssClassSet.add() previously returned null if the CssClassSet corresponded to multiple elements. In order to align with the null-safe changes in the Set interface, it will now return false instead. The same applies for CssClassSet.toggle.
EventStreamSubscription.cancel method used to return null, but since StreamSubscription.cancel has changed to be non-nullable, this method returns an empty Future instead. Due to an optimization on null Futures, this method used to complete synchronously, but now that the Future is empty instead, it completes asynchronously, therefore potentially invalidating code that relied on the synchronous side-effect. This change will only affect code using sound null-safety. See issue #41653 for more details.
Methods in Console have been updated to better reflect the modern Console specification. Particularly of interest are dir and table which take in extra optional arguments.

`dart:mirrors`

Breaking change #42714: web compilers (dart2js and DDC) now produce a compile-time error if dart:mirrors is imported.

Most projects should not be affected. Since 2.0.0 this library was unsupported and produced runtime errors on all its APIs. Since then several tools already reject code that use dart:mirrors including webdev and flutter tools, we expect few projects to run into this problem.

Tools

dartfmt

Add --fix-single-cascade-statements.
Correctly handle var in --fix-function-typedefs.
Preserve leading indentation in fixed doc comments.
Split outer nested control flow elements.
Always place a blank line after script tags.
Don't add unneeded splits on if elements near comments.
Indent blocks in initializers of multiple-variable declarations.
Update the null-aware subscript syntax from ?.[] to ?[].

Analyzer

Static analyses with a severity of "error" can no longer be ignored with comments (// ignore: code and // ignore_for_file: code).

Linter

Updated the Linter to 0.1.117, which includes:

New lint: do_not_use_environment.
New lint: exhaustive_cases.
New lint: no_default_cases (experimental).
New lint: sized_box_for_whitespace.
New lint: use_is_even_rather_than_modulo.
Updated directives_ordering to remove third party package special-casing.
Updated prefer_is_empty to special-case assert initializers and const contexts.
Updated prefer_mixin to allow "legacy" SDK abstract class mixins.
Updated sized_box_for_whitespace to address false-positives.
Updated type_annotate_public_apis to allow inferred types in final field assignments.
Updated unnecessary_lambdas to check for tear-off assignability.
Updated unsafe_html to use a SecurityLintCode (making it un-ignorable) and to include Window.open, Element.html and DocumentFragment.html in unsafe API checks. Also added checks for attributes and methods on extensions.

Dart VM

Breaking change #41100: When printing a string using the print function, the default implementation (used when not overridden by the embedder or the current zone) will print any unpaired surrogates in the string as replacement characters (U+FFFD). Similarly, the Dart_StringToUTF8 function in the Dart API will convert unpaired surrogates into replacement characters.

Pub

pub run and pub global run accepts a --enable-experiment flag enabling experiments in the Dart VM (and language).
Warn when publishing the first null-safe version of a package.
pub outdated:
- If the current version of a dependency is a prerelease version, use prereleases for latest if there is no newer stable.
- Don't require a pubspec.lock file. When the lockfile is missing, the Current column is empty.
pub upgrade: Show summary count of outdated packages after running. It will also only show newer packages if they are not prereleases or the package is already a prerelease.
Publishing Flutter plugins using the old plugin format is no longer allowed. Plugins using the old plugin format can still be consumed.
pub run: Fix precompilation with relative PUB_CACHE paths (#2486).
Preserve Windows line endings in pubspec.lock if they are already there (#2489).
Better terminal color-detection. Use colors in terminals on Windows.
Fix git folder names in cache, allowing for ssh-style git dependencies.
Fix: Avoid precompilation of dependencies of global packages.

2.8.4 - 2020-06-04

This is a patch release that fixes potential memory leaks in the Dart front-end (issues #42111 and #42112).

2.8.3 - 2020-05-28

This is a patch release that fixes the following issues:

crashes in Flutter apps (issue flutter/flutter#57318).
a regression in stack traces (issue #41907).
re-canonicalization of constants with unboxed fields (issue flutter/flutter#57190).

2.8.2 - 2020-05-13

This is a patch release that fixes an AOT compilation bug in global transformations which manifests as a NoSuchMethod exception (issue flutter/flutter#56479).

2.8.1 - 2020-05-06

Much of the changes in this release are in preparation for non-nullable types, which will arrive in a future version. In anticipation of that, we have made a number of small but technically breaking changes to several core library APIs in order to make them easier to use in a world with non-nullable types. Almost all existing Dart code will be unaffected by these changes, but if you see unexpected failures, note the breaking changes listed below.

Language

There are no new language features in this release. There are only two minor breaking changes:

Breaking change #40675: Fixed an implementation bug where local variable inference would incorrectly use the promoted type of a type variable.
Breaking change #41362: Dart 2.0.0 made the clauses implements Function, extends Function, or with Function have no effect (spec section 19.6). We fixed an implementation bug that may be visible on some rare scenarios.

Core libraries

`dart:async`

Breaking change #40676: Changed the return type of StreamSubscription.cancel() to Future<void>. Previously, it was declared to return Future and was allowed to return null at runtime.
Breaking change #40681: The runZoned() function is split into two functions: runZoned() and runZonedGuarded(), where the latter has a required onError parameter, and the former has none. This prepares the functions for null safety where the two functions will differ in the nullability of their return types.
Breaking change #40683: Errors passed to Completer.completeError(), Stream.addError(), Future.error(), etc. can no longer be null. These operations now synchronously throw an exception if passed a null error.
Make stack traces non-null #40130. Where methods like completer.completeError() allow omitting a stack trace, the platform will now insert a default stack trace rather than propagate a null value.

Error handling functions need no longer be prepared for null stack traces.

`dart:core`

Breaking change #40674: Three members on RuneIterator no longer return null when accessed before the first call to moveNext(). Instead, current and rawIndex return -1 and currentAsString returns an empty string.
Breaking change #40678: The String.fromEnvironment() default value for defaultValue is now an empty string instead of null. Likewise, the default value for int.fromEnvironment()'s defaultValue parameter is zero. Under null safety, a constructor cannot return null, so this prepares these APIs for that.
The class CastError is deprecated, and all implementation specific classes implementing TypeError or CastError now implement both. In a future release, CastError will be removed. See issue 40763 for details.
Adds StackTrace.empty constant which is the stack trace used as default stack trace when no better alternative is available.
The class TypeError no longer extends AssertionError. This also means that it no longer inherits the spurious message getter which was added to AssertionError when the second operand to assert was allowed. The value of that getter on a TypeError was the same string as returned by toString(), so it is still available.
ArgumentError.checkNotNull() and the RangeError static methods checkValueInInterval(), checkValidIndex() and checkNotNegative() all return their first argument on success. This makes these functions more convenient to use in-line in, for example, => function bodies or constructor initialization lists.

`dart:developer`

The constructors for TimelineTask now accept an optional filterKey parameter. If provided, the arguments for all events associated with the task will contain an entry named filterKey, set to the value of the filterKey parameter provided in the constructor. This will be used by tooling to allow for better filtering of timeline events.

`dart:ffi`

Breaking change: Changed Pointer.asFunction() and DynamicLibrary.lookupFunction() to extension methods. Invoking them dynamically previously already threw an exception, so the runtime behavior stays the same. However, the extension methods are only visible if dart:ffi is imported directly. This breaks code where dart:ffi is not directly imported. To fix, add:
```
import 'dart:ffi';
```

`dart:html`

Breaking change #39627: Changed the return type of several HTML native methods involving futures. In return types that matched Future<List<T>>, T was changed to dynamic. These methods would have resulted in a runtime error if they were used.
Breaking change: Node.insertAllBefore() erroneously had a return type of Node, even though it was not returning anything. This has been corrected to void.

`dart:io`

Class HttpParser will no longer throw an exception when a HTTP response status code is within [0, 999]. Customized status codes in this range are now valid.
Breaking change #33501: The signature of HttpHeaders methods add() and set have been changed to:
```
void add(String name, Object value, {bool preserveHeaderCase: false})
void set(String name, Object value, {bool preserveHeaderCase: false})
```
Setting preserveHeaderCase to true preserves the case of the name parameter instead of converting it to lowercase. The HttpHeader.forEach() method provides the current case of each header.

This is breaking only for classes extending or implementing HttpHeaders and having their own add or set methods without the bool preserveHeaderCase named parameter.
Breaking change #40702: The Socket class now throws a SocketException if the socket has been explicitly destroyed or upgraded to a secure socket upon setting or getting socket options. Previously, setting a socket option would be ignored and getting a socket option would return null.
Breaking change #40483: The Process class now throws a StateError if the process is detached (ProcessStartMode.detached and ProcessStartMode.detachedWithStdio) upon accessing the exitCode getter. It now also throws when not connected to the child process's stdio (ProcessStartMode.detached and ProcessStartMode.inheritStdio) upon accessing the stdin, stdout, and stderr getters. Previously, these getters would all return null.
Breaking change #40706: The dummy object returned if FileStat.stat() or FileStat.statSync() fail now contains Unix epoch timestamps instead of null for the accessed, changed, and modified getters.
Breaking change #40709: The HeaderValue class now parses more strictly in two invalid edge cases. This is the class used to parse the semicolon delimited parameters used in the Accept, Authorization, Content-Type, and other such HTTP headers.

The empty parameter value without double quotes (which is not allowed by the standards) is now parsed as the empty string rather than null. E.g. HeaderValue.parse("v;a=").parameters now gives {"a": ""} rather than {"a": null}.

Invalid inputs with unbalanced double quotes are now rejected. E.g. HeaderValue.parse('v;a="b').parameters will now throw a HttpException instead of giving {"a": "b"}.
The HeaderValue.toString() method now supports parameters with null values by omitting the value. HeaderValue("v", {"a": null, "b": "c"}).toString() now gives v; a; b=c. This behavior can be used to implement some features in the Accept and Sec-WebSocket-Extensions headers.

Likewise the empty value and values using characters outside of RFC 7230 tokens are now correctly implemented by double quoting such values with escape sequences. For example:
```
HeaderValue("v",
    {"a": "A", "b": "(B)", "c": "", "d": "ø", "e": "\\\""}).toString()
```
Gives: v;a=A;b="(B)";c="";d="ø";e="\\\"".
Unix domain sockets are now supported on Linux, Android and MacOS, which can be used by passing a InternetAddress of InternetAddressType.Unix into the connect(), startConnect() and bind() methods. The port argument in those methods will be ignored. The port getter always returns 0 for Unix domain sockets.
Class InternetAddressType gains one more option Unix, which represents a Unix domain address.
Class InternetAddress:
- InternetAddress constructor gains an optional type parameter. To create a Unix domain address, type is set to InternetAddressType.Unix and address is a file path.
- InternetAddress gains a new constructor fromRawAddress() that takes an address in byte format for Internet addresses or raw file path for Unix domain addresses.
Breaking change #40681: The static methods runZoned() and runWithHttpOverrides() on HttpOverrides no longer accept zoneSpecification and onError parameters. Use the runZoned() or runZonedGuarded() functions from dart:async directly if needing to specify those.
Class HttpClient and HttpServer, when receiving HttpRequest or HttpClientResponse, will now put a 8K size limit on its header fields and values.

`dart:mirrors`

Added MirrorSystem.neverType.

Dart VM

Added Dart_TypeDynamic, Dart_TypeVoid and Dart_TypeNever. Type dynamic can no longer by reached using Dart_GetType(dart:core, dynamic).
Added the following methods to the VM embedding API:
- Dart_GetNonNullableType()
- Dart_GetNullableType()
- Dart_TypeToNonNullable()
- Dart_TypeToNullable()
- Dart_IsLegacyType()
- Dart_IsNonNullableType()
- Dart_IsNullableType()

Tools

Dart Dev Compiler (DDC)

We fixed several inconsistencies between DDC and Dart2JS so that users less frequently encounter code that is accepted by one compiler but then fails in the other.

Breaking change: Deleted the legacy (analyzer based) version of DDC. For additional details see the announcement.
- The --kernel option is now ignored and defaults to true. There is no longer any way to invoke the legacy (analyzer based) version of DDC.
- Command line arguments that were only used for the legacy DDC have been removed.
- The pre-compiled dart_sdk.js artifacts generated by legacy DDC have been deleted from dart-sdk/lib/dev_compiler in favor of the versions located at dart-sdk/lib/dev_compiler/kernel.
Breaking change: Functions passed to JavaScript using the recommended package:js interop specification must now be wrapped with a call to allowInterop. This behavior was always enforced by Dart2JS, but was not enforced consistently by DDC. It is now enforced by both.
Breaking change: Constructors in @JS() classes must be marked with external. Previously the external could be omitted in some cases with DDC but doing so would cause incorrect behavior with Dart2JS.
JS interop classes with an index operator are now static errors.
All remaining support from the dart:mirrors library has been removed. Use of this library on the web has been unsupported and prevented by the Dart build systems since Dart v2.0.0. All known exception cases have been cleaned up. This change makes DDC and Dart2JS now behave consistently.

The library can still be imported on web apps, but all APIs throw. In a future breaking change release, imports to this library will likely become a compile-time error.

Dart2JS

A new representation of runtime types is enabled by default.

This change is part of a long term goal of making runtime checks cheaper and more flexible for upcoming changes in the language. The new representation disentangles how types and classes are represented and makes types first-class to the compiler. This makes it possible to do certain kind of optimizations on type checks that were not possible before and will enable us to model non-nullable types in the near future.

This change should not affect the semantics of your application, but it has some relatively small visible effects that we want to highlight:

Types are now canonicalized, this fixes a long standing bug that Types could not be used in switch cases (issue 17207).
Code-size changes may be visible, but the difference is small overall. It is more visible on smaller apps because the new implementation includes more helper methods. On large apps we have even seen an overall code-size reduction.
Certain checks are a lot faster. This is less noticeable if you are compiling apps with -O3 where checks are omitted altogether. Even with -O3, the performance of some is checks used by your app may improve.
When using -O3 and -O4 incorrect type annotations could surface as errors. The old type representation was accidentally lenient on some invalid type annotations. We have only encountered this issue on programs that were not tested properly at the js-interop program boundary.
Type.toString() has a small change that is rarely visible. For a long time, Dart2JS has had support to erase unused type variables. Today, when Dart2JS is given --lax-runtime-type-to-string (currently included in -O2, -O3, and -O4) and it decides to erase the type variable of a class Foo<T>, then it compiles expressions like foo.runtimeType.toString() to print Foo. With the new representation, this will show Foo<erased> instead. This change may be visible in error messages produced by type checks involving erased types.

Because types and classes are represented separately, we will likely reevaluate restrictions of deferred libraries in the near future. For example, we could support referring to deferred types because types can be downloaded while classes are not.

In the unlikely case you run into any issues, please file a bug so we can investigate. You can temporarily force the old type representation by passing --use-old-rti to Dart2JS if necessary, but our goal is to delete the old type representation soon.

In addition, we fixed some inconsistencies between Dart2JS and DDC:

JS interop classes with an index operator are now static errors instead of causing invalid code in Dart2JS.
Breaking change: The subtyping rule for generic functions is now more forgiving. Corresponding type parameter bounds now only need to be mutual subtypes rather than structurally equal up to renaming of bound type variables and equating all top types.
Breaking change: Types are now normalized. See normalization for the full specification. Types will now be printed in their normal form, and mutual subtypes with the same normal form will now be considered equal.
Breaking change: Constructors in @JS() classes must be marked with external. Previously, the external could be omitted for unused constructors. Omitting external for a constructor which is used would cause incorrect behavior at runtime, now omitting it on any constructor is a static error.

Other dart2js changes:

Breaking change: The --package-root flag, which was hidden and disabled in Dart 2.0.0, has been completely removed. Passing this flag will now cause dart2js to fail.

Linter

Updated the Linter to 0.1.114, which includes:

Fixed avoid_shadowing_type_parameters to support extensions and mixins.
Updated non_constant_identifier_names to allow named constructors made up of only underscores (_).
Updated avoid_unused_constructor_parameters to ignore unused params named in all underscores (_).

Analyzer

Removed support for the deprecated analysis options file name .analysis_options.

Pub

Added pub outdated command which lists outdated package dependencies, and gives advice on how to upgrade.
pub get and pub upgrade now fetch version information about hosted dependencies in parallel, improving the time package resolution performance.
pub get and pub upgrade no longer precompile executables from dependencies by default. Instead they are precompiled on first pub run. Use pub get --precompile to get the previous behavior.
Fixed missing retries of DNS failures during pub get.
If code contains imports for packages not listed in the package's pubspec.yaml then pub publish will reject the package.
pub publish no longer requires the presence of a homepage field, if the repository field is provided.
pub publish warns if non-pre-release packages depends on pre-release packages or pre-release Dart SDKs.
Relative paths in pubspec.lock now use / also on Windows to make the file sharable between machines.
Fixed language version in .dart_tool/package_config.json for packages without an explicit SDK constraint. Pub now writes an empty language version where before the language version of the current SDK would be used.
%LOCALAPPDATA% is now preferred over %APPDATA% when creating a pub cache directory on Windows. %LOCALAPPDATA% is not copied when users roam between devices.
pub publish warns if LICENSE and README.md files are not called those exact names.
pub repair cache downloads hosted packages in parallel.

2.7.2 - 2020-03-23

Security advisory: This is a patch release that addresses a vulnerability in dart:html NodeValidator related to DOM clobbering of previousSibling. See the security advisory CVE-2020-8923 for more details. Thanks to Vincenzo di Cicco for finding and reporting this issue.

This release also improves compatibility with ARMv8 processors (issue 40001) and dart:io stability (issue 40589).

2.7.1 - 2020-01-23

This is a patch release that improves dart2js compile-time (issue 40217).

Breaking change: The Dart SDK for macOS is now only available for x64 (issue 39810).

2.7.0 - 2019-12-11

Extension methods -- which we shipped in preview in 2.6.0 -- are no longer in preview, and are now officially supported as of 2.7.0. Learn more about them here:

https://medium.com/dartlang/extension-methods-2d466cd8b308

Language

Breaking change: Static extension members are accessible when imported with a prefix (issue 671). In the extension method preview launch, importing a library with a prefix hid all extension members in addition to hiding the extension name, thereby making them inaccessible in the importing library except via the explicit override syntax. Based on user feedback, we have changed this to make extensions methods accessible even when imported with a prefix.
```
```dart
  // "thing.dart"
  class Thing {
  }
  extension Show on Thing {
    void show() {
      print("This is a thing");
    }
 }
 // "client.dart"
 import "thing.dart" as p;
 void test() {
   p.Thing().show(); // Previously an error, now resolves to Show.show
 }
```
```

Core libraries

`dart:io`

Breaking change: Added IOOverrides.serverSocketBind to aid in writing tests that wish to mock ServerSocket.bind.

`dart:typed_data`

Added new constructors, .sublistView(TypedData, [start, end]) to all TypedData classes. The constructor makes it easier, and less error-prone, to create a view of (a slice of) another TypedData object.

Dart VM

New fields added to existing instances by a reload will now be initialized lazily, as if the field was a late field. This makes the initialization order program-defined, whereas previously it was undefined.

Tools

Linter

The Linter was updated to 0.1.104, which includes:

updated unnecessary_overrides to allow overrides when annotations (besides @override are specified)
updated file_names to allow names w/ leading _'s (and improved performance)
new lint: unnecessary_final

Pub

pub get generates .dart_tool/package_config.json in addition to .packages to support language versioning.
pub publish now warns about the old flutter plugin registration format.
pub publish now warns about the author field in pubspec.yaml being. obsolete.
Show a proper error message when git is not installed.

2.6.1 - 2019-11-11

This is a patch release that reduces dart2js memory usage (issue 27883), improves stability on arm64 (issue 39090) and updates the Dart FFI documentation.

2.6.0 - 2019-11-05

Language

[IN PREVIEW] Static extension members: A new language feature allowing specially declared static functions to be invoked like instance members on expressions of appropriate static types is available in preview.

Static extension members are declared using a new extension declaration. Example:

extension MyFancyList<T> on List<T> {
  /// Whether this list has an even length.
  bool get isLengthEven => this.length.isEven;

  /// Whether this list has an odd length.
  bool get isLengthOdd => !isLengthEven;

  /// List of values computed for each pairs of adjacent elements.
  ///
  /// The result always has one element less than this list,
  /// if this list has any elements.
  List<R> combinePairs<R>(R Function(T, T) combine) =>
      [for (int i = 1; i < this.length; i++)
          combine(this[i - 1], this[i])];
}

Extension declarations cannot declare instance fields or constructors. Extension members can be invoked explicitly, MyFancyList(intList).isLengthEven), or implicitly, intList.isLengthEven, where the latter is recognized by intList matching the List<T> "on" type of the declaration. An extension member cannot be called implicitly on an expression whose static type has a member with the same base-name. In that case, the interface member takes precedence. If multiple extension members apply to the same implicit invocation, the most specific one is used, if there is one such.

Extensions can be declared on any type, not just interface types.

extension IntCounter on int {
  /// The numbers from this number to, but not including, [end].
  Iterable<int> to(int end) sync* {
    int step = end < this ? -1 : 1;
    for (int i = this; i != end; i += step) yield i;
  }
}

extension CurryFunction<R, S, T> on R Function(S, T) {
  /// Curry a binary function with its first argument.
  R Function(T) curry(S first) => (T second) => this(first, second);
}

Breaking change #37985: Inference is changed when using Null values in a FutureOr context. Namely, constraints of the forms similar to Null <: FutureOr<T> now yield Null as the solution for T. For example, the following code will now print "Null", and it was printing "dynamic" before (note that the anonymous closure () {} in the example has Null as its return type):
```
import 'dart:async';

void foo<T>(FutureOr<T> Function() f) { print(T); }

main() { foo(() {}); }
```

Core libraries

Default values of parameters of abstract methods are no longer available via dart:mirrors.

`dart:developer`

Added optional parent parameter to TimelineTask constructor to allow for linking of asynchronous timeline events in the DevTools timeline view.

`dart:ffi`

Breaking change: The API now makes use of static extension members. Static extension members enable the dart:ffi API to be more precise with types, and provide convenient access to memory through extension getters and setters. The extension members on Pointer provide .value and .value = for accessing the value in native memory and [] and []= for indexed access. The method asExternalTypedData has been replaced with asTypedList extension methods. And finally, Structs do no longer have a type argument and are accessed using the extension member .ref on Pointer. These changes makes the code using dart:ffi much more concise.
Breaking change: The memory management has been removed (Pointer.allocate and Pointer.free). Instead, memory management is available in package:ffi.
Breaking change: Pointer.offsetBy was removed, use cast and elementAt instead.
Faster memory load and stores.
The dartanalyzer (commandline and IDEs) now reports dart:ffi static errors.
Callbacks are now supported in AOT (ahead-of-time) compiled code.

`dart:io`

Added enableTimelineLogging property to HttpClient which, when enabled, will post HTTP connection and request information to the developer timeline for all HttpClient instances.

Dart VM

Added a new tool for AOT compiling Dart programs to native, self-contained executables. See https://dart.dev/tools/dart2native for additional details.

Dart for the Web

Dart Dev Compiler (DDC)

Kernel DDC will no longer accept non-dill files as summary inputs.
Removed support for the deprecated web extension.

Tools

Linter

The Linter was updated to 0.1.101, which includes:

fixed diagnostic_describe_all_properties to flag properties in Diagnosticables with no debug methods defined
fixed noSuchMethod exception in camel_case_extensions when analyzing unnamed extensions
fixed avoid_print to catch tear-off usage
new lint: avoid_web_libraries_in_flutter (experimental)
(internal) prepare unnecessary_lambdas for coming MethodInvocation vs. FunctionExpressionInvocation changes

2.5.2 - 2019-10-08

This is a patch release with properly signed binaries required for macOS Catalina (Issue 38765).

2.5.1 - 2019-09-27

This is a patch release that prevents type inference failures in the analyzer (Issue 38365).

2.5.0 - 2019-09-10

Language

The set of operations allowed in constant expressions has been expanded as described in the constant update proposal. The control flow and spread collection features shipped in Dart 2.3 are now also supported in constants as described in the specification here.

Specifically, it is now valid to use the following operations in constant expressions under the appropriate conditions:

Casts (e as T) and type tests (e is T).
Comparisons to null, even for types which override the == operator.
The &, |, and ^ binary operators on booleans.
The spread operators (... and ...?).
An if element in a collection literal.

// Example: these are now valid constants.
const Object i = 3;
const list = [i as int];
const set = {if (list is List<int>) ...list};
const map = {if (i is int) i : "int"};

In addition, the semantics of constant evaluation has been changed as follows:

The && operator only evaluates its second operand if the first evaluates to true.
The || operator only evaluates its second operand if the first evaluates to false.
The ?? operator only evaluates its second operand if the first evaluates to null.
The conditional operator (e ? e1 : e2) only evaluates one of the two branches, depending on the value of the first operand.

// Example: x is now a valid constant definition.
const String s = null;
const int x = (s == null) ? 0 : s.length;

Core libraries

Breaking change #36900: The following methods and properties across various core libraries, which used to declare a return type of List<int>, were updated to declare a return type of Uint8List:
- BytesBuilder.takeBytes()
- BytesBuilder.toBytes()
- Datagram.data
- File.readAsBytes() (Future<Uint8List>)
- File.readAsBytesSync()
- InternetAddress.rawAddress
- RandomAccessFile.read() (Future<Uint8List>)
- RandomAccessFile.readSync()
- RawSocket.read()
- Utf8Codec.encode() (and Utf8Encoder.convert())
In addition, the following classes were updated to implement Stream<Uint8List> rather than Stream<List<int>>:
- HttpRequest
- Socket
Possible errors and how to fix them
- The argument type 'Utf8Decoder' can't be assigned to the parameter type 'StreamTransformer<Uint8List, dynamic>'
  
  type 'Utf8Decoder' is not a subtype of type 'StreamTransformer' of 'streamTransformer'"
  
  You can fix these call sites by updating your code to use StreamTransformer.bind() instead of Stream.transform(), like so:
  
  Before: stream.transform(utf8.decoder) After: utf8.decoder.bind(stream)
- The argument type 'IOSink' can't be assigned to the parameter type 'StreamConsumer'
  
  type '_IOSinkImpl' is not a subtype of type 'StreamConsumer' of 'streamConsumer'
  
  You can fix these call sites by casting your stream instance to a Stream<List<int>> before calling .pipe() on the stream, like so:
  
  Before: stream.pipe(consumer) After: stream.cast<List<int>>().pipe(consumer)
Finally, the following typed lists were updated to have their sublist() methods declare a return type that is the same as the source list:
- Int8List.sublist() → Int8List
- Int16List.sublist() → Int16List
- Int32List.sublist() → Int32List
- Int64List.sublist() → Int64List
- Int32x4List.sublist() → Int32x4List
- Float32List.sublist() → Float32List
- Float64List.sublist() → Float64List
- Float32x4List.sublist() → Float32x4List
- Float64x2List.sublist() → Float64x2List
- Uint8List.sublist() → Uint8List
- Uint8ClampedList.sublist() → Uint8ClampedList
- Uint16List.sublist() → Uint16List
- Uint32List.sublist() → Uint32List
- Uint64List.sublist() → Uint64List

`dart:async`

Add value and error constructors on Stream to allow easily creating single-value or single-error streams.

`dart:core`

Update Uri class to support RFC6874: "%25" or "%" can be appended to the end of a valid IPv6 representing a Zone Identifier. A valid zone ID consists of unreversed character or Percent encoded octet, which was defined in RFC3986. IPv6addrz = IPv6address "%25" ZoneID

`dart:io`

Breaking change #37192: The Cookie class's constructor's name and value optional positional parameters are now mandatory. The signature changes from:
```
Cookie([String name, String value])
```
to
```
Cookie(String name, String value)
```
However, it has not been possible to set name and value to null since Dart 1.3.0 (2014) where a bug made it impossible. Any code not using both parameters or setting any to null would necessarily get a noSuchMethod exception at runtime. This change catches such erroneous uses at compile time. Since code could not previously correctly omit the parameters, this is not really a breaking change.
Breaking change #37192: The Cookie class's name and value setters now validates that the strings are made from the allowed character set and are not null. The constructor already made these checks and this fixes the loophole where the setters didn't also validate.

Dart VM

Tools

Pub

Clean-up invalid git repositories in cache when fetching from git.
Breaking change #36765: Packages published to pub.dev can no longer contain git dependencies. These packages will be rejected by the server.

Linter

The Linter was updated to 0.1.96, which includes:

fixed false positives in unnecessary_parens
various changes to migrate to preferred analyzer APIs
rule test fixes

Dartdoc

Dartdoc was updated to 0.28.4; this version includes several fixes and is based on a newer version of the analyzer package.

2.4.1 - 2019-08-07

This is a patch release that fixes a performance regression in JIT mode, as well as a potential crash of our AOT compiler.

Dart VM

Fixed a performance regression where usage of Int32List could trigger repeated deoptimizations in JIT mode (Issue 37551).
Fixed a bug where usage of a static getter with name length could cause a crash in our AOT compiler (Issue 35121).

Dart Dev Compiler (DDC)

Callbacks passed to JS and wrapped with allowInterop or allowInteropCaptureThis are now strict about argument counts and argument types. This may mean that tests which were previously passing and relying on loose argument checking (too many or too few arguments, or arguments with too specific types like List<Something> instead of List<dynamic>) may start failing. This changes makes DDC behave more like dart2js with the default flags.

2.4.0 - 2019-06-27

Core libraries

`dart:isolate`

TransferableTypedData class was added to facilitate faster cross-isolate communication of Uint8List data.
Breaking change: Isolate.resolvePackageUri will always throw an UnsupportedError when compiled with dart2js or DDC. This was the only remaining API in dart:isolate that didn't automatically throw since we dropped support for this library in Dart 2.0.0. Note that the API already throws in dart2js if the API is used directly without manually setting up a defaultPackagesBase hook.

`dart:developer`

Exposed result, errorCode and errorDetail getters in ServiceExtensionResponse to allow for better debugging of VM service extension RPC results.

`dart:io`

Fixed Cookie class interoperability with certain websites by allowing the cookie values to be the empty string (Issue 35804) and not stripping double quotes from the value (Issue 33327) in accordance with RFC 6265.
#36971: The HttpClientResponse interface has been extended with the addition of a new compressionState getter, which specifies whether the body of a response was compressed when it was received and whether it has been automatically uncompressed via HttpClient.autoUncompress.

As part of this change, a corresponding new enum was added to dart:io: HttpClientResponseCompressionState.

This is a breaking change for those implementing the HttpClientResponse interface as subclasses will need to implement the new getter.

`dart:async`

Breaking change #36382: The await for allowed null as a stream due to a bug in StreamIterator class. This bug has now been fixed.

`dart:core`

#36171: The RegExp interface has been extended with two new constructor named parameters:
- unicode: (bool, default: false), for Unicode patterns
- dotAll: (bool, default: false), to change the matching behavior of '.' to also match line terminating characters.
Appropriate properties for these named parameters have also been added so their use can be detected after construction.

In addition, RegExp methods that originally returned Match objects now return a more specific subtype, RegExpMatch, which adds two features:
- Iterable<String> groupNames, a property that contains the names of all named capture groups
- String namedGroup(String name), a method that retrieves the match for the given named capture group
This is a breaking change for implementers of the RegExp interface. Subclasses will need to add the new properties and may have to update the return types on overridden methods.

Language

Breaking change #35097: Covariance of type variables used in super-interfaces is now enforced. For example, the following code was previously accepted and will now be rejected:

class A<X> {};
class B<X> extends A<void Function(X)> {};

The identifier async can now be used in asynchronous and generator functions.

Dart for the Web

Dart Dev Compiler (DDC)

Improve NoSuchMethod errors for failing dynamic calls. Now they include specific information about the nature of the error such as:
- Attempting to call a null value.
- Calling an object instance with a null call() method.
- Passing too few or too many arguments.
- Passing incorrect named arguments.
- Passing too few or too many type arguments.
- Passing type arguments to a non-generic method.

Tools

Linter

The Linter was updated to 0.1.91, which includes the following changes:

Fixed missed cases in prefer_const_constructors
Fixed prefer_initializing_formals to no longer suggest API breaking changes
Updated omit_local_variable_types to allow explicit dynamics
Fixed null-reference in unrelated_type_equality_checks
New lint: unsafe_html
Broadened prefer_null_aware_operators to work beyond local variables.
Added prefer_if_null_operators.
Fixed prefer_contains false positives.
Fixed unnecessary_parenthesis false positives.
Fixed prefer_asserts_in_initializer_lists false positives
Fixed curly_braces_in_flow_control_structures to handle more cases
New lint: prefer_double_quotes
New lint: sort_child_properties_last
Fixed type_annotate_public_apis false positive for static const initializers

Pub

pub publish will no longer warn about missing dependencies for import statements in example/.
OAuth2 authentication will explicitly ask for the openid scope.

2.3.2 - 2019-06-11

This is a patch version release with a security improvement.

Security vulnerability

Security improvement: On Linux and Android, starting a process with Process.run, Process.runSync, or Process.start would first search the current directory before searching PATH (Issue 37101). This behavior effectively put the current working directory in the front of PATH, even if it wasn't in the PATH. This release changes that behavior to only searching the directories in the PATH environment variable. Operating systems other than Linux and Android didn't have this behavior and aren't affected by this vulnerability.

This vulnerability could result in execution of untrusted code if a command without a slash in its name was run inside an untrusted directory containing an executable file with that name:
```
Process.run("ls", workingDirectory: "/untrusted/directory")
```
This would attempt to run /untrusted/directory/ls if it existed, even though it is not in the PATH. It was always safe to instead use an absolute path or a path containing a slash.

This vulnerability was introduced in Dart 2.0.0.

2.3.1 - 2019-05-21

This is a patch version release with bug fixes.

Tools

dart2js

Fixed a bug that caused the compiler to crash when it compiled UI-as-code features within fields (Issue 36864).

2.3.0 - 2019-05-08

The focus in this release is on the new "UI-as-code" language features which make collections more expressive and declarative.

Language

Flutter is growing rapidly, which means many Dart users are building UI in code out of big deeply-nested expressions. Our goal with 2.3.0 was to make that kind of code easier to write and maintain. Collection literals are a large component, so we focused on three features to make collections more powerful. We'll use list literals in the examples below, but these features also work in map and set literals.

Spread

Placing ... before an expression inside a collection literal unpacks the result of the expression and inserts its elements directly inside the new collection. Where before you had to write something like this:

CupertinoPageScaffold(
  child: ListView(children: [
    Tab2Header()
  ]..addAll(buildTab2Conversation())
    ..add(buildFooter())),
);

Now you can write this:

CupertinoPageScaffold(
  child: ListView(children: [
    Tab2Header(),
    ...buildTab2Conversation(),
    buildFooter()
  ]),
);

If you know the expression might evaluate to null and you want to treat that as equivalent to zero elements, you can use the null-aware spread ...?.

Collection if

Sometimes you might want to include one or more elements in a collection only under certain conditions. If you're lucky, you can use a ?: operator to selectively swap out a single element, but if you want to exchange more than one or omit elements, you are forced to write imperative code like this:

Widget build(BuildContext context) {
  var children = [
    IconButton(icon: Icon(Icons.menu)),
    Expanded(child: title)
  ];

  if (isAndroid) {
    children.add(IconButton(icon: Icon(Icons.search)));
  }

  return Row(children: children);
}

We now allow if inside collection literals to conditionally omit or (with else) swap out an element:

Widget build(BuildContext context) {
  return Row(
    children: [
      IconButton(icon: Icon(Icons.menu)),
      Expanded(child: title),
      if (isAndroid)
        IconButton(icon: Icon(Icons.search)),
    ],
  );
}

Unlike the existing ?: operator, a collection if can be composed with spreads to conditionally include or omit multiple items:

Widget build(BuildContext context) {
  return Row(
    children: [
      IconButton(icon: Icon(Icons.menu)),
      if (isAndroid) ...[
        Expanded(child: title),
        IconButton(icon: Icon(Icons.search)),
      ]
    ],
  );
}

Collection for

In many cases, the higher-order methods on Iterable give you a declarative way to modify a collection in the context of a single expression. But some operations, especially involving both transforming and filtering, can be cumbersome to express in a functional style.

To solve this problem, you can use for inside a collection literal. Each iteration of the loop produces an element which is then inserted in the resulting collection. Consider the following code:

var command = [
  engineDartPath,
  frontendServer,
  ...fileSystemRoots.map((root) => "--filesystem-root=$root"),
  ...entryPoints
      .where((entryPoint) => fileExists("lib/$entryPoint.json"))
      .map((entryPoint) => "lib/$entryPoint"),
  mainPath
];

With a collection for, the code becomes simpler:

var command = [
  engineDartPath,
  frontendServer,
  for (var root in fileSystemRoots) "--filesystem-root=$root",
  for (var entryPoint in entryPoints)
    if (fileExists("lib/$entryPoint.json")) "lib/$entryPoint",
  mainPath
];

As you can see, all three of these features can be freely composed. For full details of the changes, see the official proposal.

Note: These features are not currently supported in const collection literals. In a future release, we intend to relax this restriction and allow spread and collection if inside const collections.

Core library changes

`dart:isolate`

Added debugName property to Isolate.
Added debugName optional parameter to Isolate.spawn and Isolate.spawnUri.

`dart:core`

RegExp patterns can now use lookbehind assertions.
RegExp patterns can now use named capture groups and named backreferences. Currently, named group matches can only be retrieved in Dart either by the implicit index of the named group or by downcasting the returned Match object to the type RegExpMatch. The RegExpMatch interface contains methods for retrieving the available group names and retrieving a match by group name.

Dart VM

The VM service now requires an authentication code by default. This behavior can be disabled by providing the --disable-service-auth-codes flag.
Support for deprecated flags '-c' and '--checked' has been removed.

Dart for the Web

dart2js

A binary format was added to dump-info. The old JSON format is still available and provided by default, but we are starting to deprecate it. The new binary format is more compact and cheaper to generate. On some large apps we tested, it was 4x faster to serialize and used 6x less memory.

To use the binary format today, use --dump-info=binary, instead of --dump-info.

What to expect next?

The visualizer tool will not be updated to support the new binary format, but you can find several command-line tools at package:dart2js_info that provide similar features to those in the visualizer.
The command-line tools in package:dart2js_info also work with the old JSON format, so you can start using them even before you enable the new format.
In a future release --dump-info will default to --dump-info=binary. At that point, there will be an option to fallback to the JSON format, but the visualizer tool will be deprecated.
A release after that, the JSON format will no longer be available from dart2js, but may be available from a command-line tool in package:dart2js_info.

Tools

dartfmt

Tweak set literal formatting to follow other collection literals.
Add support for "UI as code" features.
Properly format trailing commas in assertions.
Improve indentation of adjacent strings in argument lists.

Linter

The Linter was updated to 0.1.86, which includes the following changes:

Added the following lints: prefer_inlined_adds, prefer_for_elements_to_map_fromIterable, prefer_if_elements_to_conditional_expressions, diagnostic_describe_all_properties.
Updated file_names to skip prefixed-extension Dart files (.css.dart, .g.dart, etc.).
Fixed false positives in unnecessary_parenthesis.

Pub

Added a CHANGELOG validator that complains if you pub publish without mentioning the current version.
Removed validation of library names when doing pub publish.
Added support for pub global activateing package from a custom pub URL.
Added subcommand: pub logout. Logs you out of the current session.

Dart native

Initial support for compiling Dart apps to native machine code has been added. Two new tools have been added to the bin folder of the Dart SDK:

dart2aot: AOT (ahead-of-time) compiles a Dart program to native machine code. The tool is supported on Windows, macOS, and Linux.
dartaotruntime: A small runtime used for executing an AOT compiled program.

2.2.0 - 2019-02-26

Language

Sets now have a literal syntax like lists and maps do:

var set = {1, 2, 3};

Using curly braces makes empty sets ambiguous with maps:

var collection = {}; // Empty set or map?

To avoid breaking existing code, an ambiguous literal is treated as a map. To create an empty set, you can rely on either a surrounding context type or an explicit type argument:

// Variable type forces this to be a set:
Set<int> set = {};

// A single type argument means this must be a set:
var set2 = <int>{};

Set literals are released on all platforms. The set-literals experiment flag has been disabled.

Tools

Analyzer

The DEPRECATED_MEMBER_USE hint was split into two hints:
- DEPRECATED_MEMBER_USE reports on usage of @deprecated members declared in a different package.
- DEPRECATED_MEMBER_USE_FROM_SAME_PACKAGE reports on usage of @deprecated members declared in the same package.

Linter

Upgraded the linter to 0.1.82 which adds the following improvements:

Added provide_deprecation_message, and use_full_hex_values_for_flutter_colors, prefer_null_aware_operators.
Fixed prefer_const_declarations set literal false-positives.
Updated prefer_collection_literals to support set literals.
Updated unnecessary_parenthesis play nicer with cascades.
Removed deprecated lints from the "all options" sample.
Stopped registering "default lints".
Fixed hash_and_equals to respect hashCode fields.

Other libraries

`package:kernel`

Breaking change: The klass getter on the InstanceConstant class in the Kernel AST API has been renamed to classNode for consistency.
Breaking change: Updated Link implementation to utilize true symbolic links instead of junctions on Windows. Existing junctions will continue to work with the new Link implementation, but all new links will create symbolic links.

To create a symbolic link, Dart must be run with administrative privileges or Developer Mode must be enabled, otherwise a FileSystemException will be raised with errno set to ERROR_PRIVILEGE_NOT_HELD (Issue 33966).

2.1.1 - 2019-02-18

This is a patch version release. Again, the team's focus was mostly on improving performance and stability after the large changes in Dart 2.0.0. In particular, dart2js now always uses the "fast startup" emitter and the old emitter has been removed.

There are a couple of very minor breaking changes:

In dart:io, adding to a closed IOSink now throws a StateError.
On the Dart VM, a soundness hole when using dart:mirrors to reflectively invoke a method in an incorrect way that violates its static types has been fixed (Issue 35611).

Language

This release has no language changes.

Core library

`dart:core`

Made DateTime.parse() also recognize , as a valid decimal separator when parsing from a string (Issue 35576).

`dart:html`

Added methods Element.removeAttribute, Element.removeAttributeNS, Element.hasAttribute and Element.hasAttributeNS. (Issue 35655).
Improved dart2js compilation of element.attributes.remove(name) to generate element.removeAttribute(name), so that there is no performance reason to migrate to the above methods.
Fixed a number of dart:html bugs:
- Fixed HTML API's with callback typedef to correctly convert Dart functions to JS functions (Issue 35484).
- HttpStatus constants exposed in dart:html (Issue 34318).
- Expose DomName ondblclick and dblclickEvent for Angular analyzer.
- Fixed removeAll on classes; elements parameter should be Iterable<Object> to match Set's removeAll not Iterable<E> (Issue 30278).
- Fixed a number of methods on DataTransferItem, Entry, FileEntry and DirectoryEntry which previously returned NativeJavaScriptObject. This fixes handling drag/drop of files/directories (Issue 35510).
- Added ability to allow local file access from Chrome browser in ddb.

`dart:io`

Breaking change: Adding to a closed IOSink now throws a StateError.
Added ability to get and set low level socket options.

Dart VM

In previous releases it was possible to violate static types using dart:mirrors. This code would run without any TypeErrors and print "impossible" output:

import 'dart:mirrors';

class A {
  void method(int v) {
    if (v != null && v is! int) {
      print("This should be impossible: expected null or int got ${v}");
    }
  }
}

void main() {
  final obj = A();
  reflect(obj).invoke(#method, ['not-an-number']);
}

This bug is fixed now. Only code that already violates static typing will break. See Issue 35611 for more details.

Dart for the Web

dart2js

The old "full emitter" back-end is removed and dart2js always uses the "fast startup" back-end. The generated fast startup code is optimized to load faster, even though it can be slightly larger. The --fast-startup and --no-fast-startup are allowed but ignored. They will be removed in a future version.
We fixed a bug in how deferred constructor calls were incorrectly not marked as deferred. The old behavior didn't cause breakages, but was imprecise and pushed more code to the main output unit.
A new deferred split algorithm implementation was added.

This implementation fixes a soundness bug and addresses performance issues of the previous implementation, because of that it can have a visible impact on apps. In particular:
- We fixed a performance issue which was introduced when we migrated to the common front-end. On large apps, the fix can cut 2/3 of the time spent on this task.
- We fixed a bug in how inferred types were categorized (Issue 35311). The old behavior was unsound and could produce broken programs. The fix may cause more code to be pulled into the main output unit.
  
  This shows up frequently when returning deferred values from closures since the closure's inferred return type is the deferred type. For example, if you have:
```
() async {
  await deferred_prefix.loadLibrary();
  return new deferred_prefix.Foo();
}
```
  The closure's return type is Future<Foo>. The old implementation defers Foo, and incorrectly makes the return type Future<dynamic>. This may break in places where the correct type is expected.
  
  The new implementation will not defer Foo, and will place it in the main output unit. If your intent is to defer it, then you need to ensure the return type is not inferred to be Foo. For example, you can do so by changing the code to a named closure with a declared type, or by ensuring that the return expression has the type you want, like:
```
() async {
  await deferred_prefix.loadLibrary();
  return new deferred_prefix.Foo() as dynamic;
}
```
  Because the new implementation might require you to inspect and fix your app, we exposed two temporary flags:
- The --report-invalid-deferred-types causes dart2js to run both the old and new algorithms and report any cases where an invalid type was detected.
- The --new-deferred-split flag enables this new algorithm.
The --categories=* flag is being replaced. --categories=all was only used for testing and it is no longer supported. --categories=Server continues to work at this time but it is deprecated, please use --server-mode instead.
The --library-root flag was replaced by --libraries-spec. This flag is rarely used by developers invoking dart2js directly. It's important for integrating dart2js with build systems. See --help for more details on the new flag.

Tools

Analyzer

Support for declarations-casts has been removed and the implicit-casts option now has the combined semantics of both options. This means that users that disable implicit-casts might now see errors that were not previously being reported.
New hints added:
- NON_CONST_CALL_TO_LITERAL_CONSTRUCTOR and NON_CONST_CALL_TO_LITERAL_CONSTRUCTOR_USING_NEW inform you when a @literal const constructor is called in a non-const context (or with new).
- INVALID_LITERAL_ANNOTATION reports when something other than a const constructor is annotated with @literal.
- SUBTYPE_OF_SEALED_CLASS reports when any class or mixin subclasses (extends, implements, mixes in, or constrains to) a @sealed class, and the two are declared in different packages.
- MIXIN_ON_SEALED_CLASS reports when a @sealed class is used as a superclass constraint of a mixin.

dartdoc

Default styles now work much better on mobile. Simple browsing and searching of API docs now work in many cases.

Upgraded the linter to 0.1.78 which adds the following improvements:

Added prefer_final_in_for_each, unnecessary_await_in_return, use_function_type_syntax_for_parameters, avoid_returning_null_for_future, and avoid_shadowing_type_parameters.
Updated invariant_booleans status to experimental.
Fixed type_annotate_public_apis false positives on local functions.
Fixed avoid_shadowing_type_parameters to report shadowed type parameters in generic typedefs.
Fixed use_setters_to_change_properties to not wrongly lint overriding methods.
Fixed cascade_invocations to not lint awaited targets.
Fixed prefer_conditional_assignment false positives.
Fixed join_return_with_assignment false positives.
Fixed cascade_invocations false positives.
Deprecated prefer_bool_in_asserts as it is redundant in Dart 2.

2.1.0 - 2018-11-15

This is a minor version release. The team's focus was mostly on improving performance and stability after the large changes in Dart 2.0.0. Notable changes:

We've introduced a dedicated syntax for declaring a mixin. Instead of the class keyword, it uses mixin:
```
mixin SetMixin<E> implements Set<E> {
  ...
}
```
The new syntax also enables super calls inside mixins.
Integer literals now work in double contexts. When passing a literal number to a function that expects a double, you no longer need an explicit .0 at the end of the number. In releases before 2.1, you need code like this when setting a double like fontSize:
```
TextStyle(fontSize: 18.0)
```
Now you can remove the .0:
```
TextStyle(fontSize: 18)
```
In releases before 2.1, fontSize : 18 causes a static error. This was a common mistake and source of friction.
Breaking change: A number of static errors that should have been detected and reported were not supported in 2.0.0. These are reported now, which means existing incorrect code may show new errors.
dart:core now exports Future and Stream. You no longer need to import dart:async to use those very common types.

Language

Introduced a new syntax for mixin declarations.
```
mixin SetMixin<E> implements Set<E> {
  ...
}
```
Most classes that are intended to be used as mixins are intended to only be used as mixins. The library author doesn't want users to be able to construct or subclass the class. The new syntax makes that intent clear and enforces it in the type system. It is an error to extend or construct a type declared using mixin. (You can implement it since mixins expose an implicit interface.)

Over time, we expect most mixin declarations to use the new syntax. However, if you have a "mixin" class where users are extending or constructing it, note that moving it to the new syntax is a breaking API change since it prevents users from doing that. If you have a type like this that is a mixin as well as being a concrete class and/or superclass, then the existing syntax is what you want.

If you need to use a super inside a mixin, the new syntax is required. This was previously only allowed with the experimental --supermixins flag because it has some complex interactions with the type system. The new syntax addresses those issues and lets you use super calls by declaring the superclass constraint your mixin requires:
```
class Superclass {
  superclassMethod() {
    print("in superclass");
  }
}

mixin SomeMixin on Superclass {
  mixinMethod() {
    // This is OK:
    super.superclassMethod();
  }
}

class GoodSub extends Superclass with SomeMixin {}

class BadSub extends Object with SomeMixin {}
// Error: Since the super() call in mixinMethod() can't find a
// superclassMethod() to call, this is prohibited.
```
Even if you don't need to use super calls, the new mixin syntax is good because it clearly expresses that you intend the type to be mixed in.
Allow integer literals to be used in double contexts. An integer literal used in a place where a double is required is now interpreted as a double value. The numerical value of the literal needs to be precisely representable as a double value.
Integer literals compiled to JavaScript are now allowed to have any value that can be exactly represented as a JavaScript Number. They were previously limited to such numbers that were also representable as signed 64-bit integers.

(Breaking) A number of static errors that should have been detected and reported were not supported in 2.0.0. These are reported now, which means existing incorrect code may show new errors:

Setters with the same name as the enclosing class aren't allowed. (Issue 34225.) It is not allowed to have a class member with the same name as the enclosing class:
```
class A {
  set A(int x) {}
}
```
Dart 2.0.0 incorrectly allows this for setters (only). Dart 2.1.0 rejects it.

To fix: This is unlikely to break anything, since it violates all style guides anyway.
Constant constructors cannot redirect to non-constant constructors. (Issue 34161.) It is not allowed to have a constant constructor that redirects to a non-constant constructor:
```
class A {
  const A.foo() : this(); // Redirecting to A()
  A() {}
}
```
Dart 2.0.0 incorrectly allows this. Dart 2.1.0 rejects it.

To fix: Make the target of the redirection a properly const constructor.
Abstract methods may not unsoundly override a concrete method. (Issue 32014.) Concrete methods must be valid implementations of their interfaces:
```
class A {
  num get thing => 2.0;
}

abstract class B implements A {
  int get thing;
}

class C extends A with B {}
// 'thing' from 'A' is not a valid override of 'thing' from 'B'.

main() {
  print(new C().thing.isEven); // Expects an int but gets a double.
}
```
Dart 2.0.0 allows unsound overrides like the above in some cases. Dart 2.1.0 rejects them.

To fix: Relax the type of the invalid override, or tighten the type of the overridden method.
Classes can't implement FutureOr. (Issue 33744.) Dart doesn't allow classes to implement the FutureOr type:
```
class A implements FutureOr<Object> {}
```
Dart 2.0.0 allows classes to implement FutureOr. Dart 2.1.0 does not.

To fix: Don't do this.
Type arguments to generic typedefs must satisfy their bounds. (Issue 33308.) If a parameterized typedef specifies a bound, actual arguments must be checked against it:
```
class A<X extends int> {}

typedef F<Y extends int> = A<Y> Function();

F<num> f = null;
```
Dart 2.0.0 allows bounds violations like F<num> above. Dart 2.1.0 rejects them.

To fix: Either remove the bound on the typedef parameter, or pass a valid argument to the typedef.
Constructor invocations must use valid syntax, even with optional new. (Issue 34403.) Type arguments to generic named constructors go after the class name, not the constructor name, even when used without an explicit new:
```
class A<T> {
  A.foo() {}
}

main() {
  A.foo<String>(); // Incorrect syntax, was accepted in 2.0.0.
  A<String>.foo(); // Correct syntax.
}
```
Dart 2.0.0 accepts the incorrect syntax when the new keyword is left out. Dart 2.1.0 correctly rejects this code.

To fix: Move the type argument to the correct position after the class name.
Instance members should shadow prefixes. (Issue 34498.) If the same name is used as an import prefix and as a class member name, then the class member name takes precedence in the class scope.
```
import 'dart:core';
import 'dart:core' as core;

class A {
  core.List get core => null; // "core" refers to field, not prefix.
}
```
Dart 2.0.0 incorrectly resolves the use of core in core.List to the prefix name. Dart 2.1.0 correctly resolves this to the field name.

To fix: Change the prefix name to something which does not clash with the instance member.
Implicit type arguments in extends clauses must satisfy the class bounds. (Issue 34532.) Implicit type arguments for generic classes are computed if not passed explicitly, but when used in an extends clause they must be checked for validity:
```
class Foo<T> {}

class Bar<T extends Foo<T>> {}

class Baz extends Bar {} // Should error because Bar completes to Bar<Foo>
```
Dart 2.0.0 accepts the broken code above. Dart 2.1.0 rejects it.

To fix: Provide explicit type arguments to the superclass that satisfy the bound for the superclass.
Mixins must correctly override their superclasses. (Issue 34235.) In some rare cases, combinations of uses of mixins could result in invalid overrides not being caught:
```
class A {
  num get thing => 2.0;
}

class M1 {
  int get thing => 2;
}

class B = A with M1;

class M2 {
  num get thing => 2.0;
}

class C extends B with M2 {} // 'thing' from 'M2' not a valid override.

main() {
  M1 a = new C();
  print(a.thing.isEven); // Expects an int but gets a double.
}
```
Dart 2.0.0 accepts the above example. Dart 2.1.0 rejects it.

To fix: Ensure that overriding methods are correct overrides of their superclasses, either by relaxing the superclass type, or tightening the subclass/mixin type.

Core libraries

`dart:async`

Fixed a bug where calling stream.take(0).drain(value) would not correctly forward the value through the returned Future.
Added a StreamTransformer.fromBind constructor.
Updated Stream.fromIterable to send a done event after the error when the iterator's moveNext throws, and handle if the current getter throws (issue 33431).

`dart:core`

Added HashMap.fromEntries and LinkedHashmap.fromEntries constructors.
Added ArgumentError.checkNotNull utility method.
Made Uri parsing more permissive about [ and ] occurring in the path, query or fragment, and # occurring in fragment.
Exported Future and Stream from dart:core.
Added operators &, | and ^ to bool.
Added missing methods to UnmodifiableMapMixin. Some maps intended to be unmodifiable incorrectly allowed new methods added in Dart 2 to succeed.
Deprecated the provisional annotation and the Provisional annotation class. These should have been removed before releasing Dart 2.0, and they have no effect.

`dart:html`

Fixed Service Workers and any Promise/Future API with a Dictionary parameter.

APIs in dart:html (that take a Dictionary) will receive a Dart Map parameter. The Map parameter must be converted to a Dictionary before passing to the browser's API. Before this change, any Promise/Future API with a Map/Dictionary parameter never called the Promise and didn't return a Dart Future - now it does.

This caused a number of breaks especially in Service Workers (register, etc.). Here is a complete list of the fixed APIs:

BackgroundFetchManager
- Future<BackgroundFetchRegistration> fetch(String id, Object requests, [Map options])
CacheStorage
- Future match(/*RequestInfo*/ request, [Map options])
CanMakePayment
- Future<List<Client>> matchAll([Map options])
CookieStore
- Future getAll([Map options])
- Future set(String name, String value, [Map options])
CredentialsContainer
- Future get([Map options])
- Future create([Map options])
ImageCapture
- Future setOptions(Map photoSettings)
MediaCapabilities
- Future<MediaCapabilitiesInfo> decodingInfo(Map configuration)
- Future<MediaCapabilitiesInfo> encodingInfo(Map configuration)
MediaStreamTrack
- Future applyConstraints([Map constraints])
Navigator
- Future requestKeyboardLock([List<String> keyCodes])
- Future requestMidiAccess([Map options])
- Future share([Map data])
OffscreenCanvas
- Future<Blob> convertToBlob([Map options])
PaymentInstruments
- Future set(String instrumentKey, Map details)
Permissions
- Future<PermissionStatus> query(Map permission)
- Future<PermissionStatus> request(Map permissions)
- Future<PermissionStatus> revoke(Map permission)
PushManager
- Future permissionState([Map options])
- Future<PushSubscription> subscribe([Map options])

RtcPeerConnection

Changed:

Future createAnswer([options_OR_successCallback,
    RtcPeerConnectionErrorCallback failureCallback,
    Map mediaConstraints])

to:

Future<RtcSessionDescription> createAnswer([Map options])

Changed:

Future createOffer([options_OR_successCallback,
    RtcPeerConnectionErrorCallback failureCallback,
    Map rtcOfferOptions])

to:

Future<RtcSessionDescription> createOffer([Map options])

Changed:

Future setLocalDescription(Map description,
    VoidCallback successCallback,
    [RtcPeerConnectionErrorCallback failureCallback])

to:

Future setLocalDescription(Map description)

Changed:

Future setLocalDescription(Map description,
    VoidCallback successCallback,
    [RtcPeerConnectionErrorCallback failureCallback])

to:

Future setRemoteDescription(Map description)

ServiceWorkerContainer
- Future<ServiceWorkerRegistration> register(String url, [Map options])
ServiceWorkerRegistration
- Future<List<Notification>> getNotifications([Map filter])
- Future showNotification(String title, [Map options])
VRDevice
- Future requestSession([Map options])
- Future supportsSession([Map options])
VRSession
- Future requestFrameOfReference(String type, [Map options])
Window
- Future fetch(/*RequestInfo*/ input, [Map init])
WorkerGlobalScope
- Future fetch(/*RequestInfo*/ input, [Map init])

In addition, exposed Service Worker "self" as a static getter named "instance". The instance is exposed on four different Service Worker classes and can throw a InstanceTypeError if the instance isn't of the class expected (WorkerGlobalScope.instance will always work and not throw):

SharedWorkerGlobalScope.instance
DedicatedWorkerGlobalScope.instance
ServiceWorkerGlobalScope.instance
WorkerGlobalScope.instance

`dart:io`

Added new HTTP status codes.

Dart for the Web

dart2js

(Breaking) Duplicate keys in a const map are not allowed and produce a compile-time error. Dart2js used to report this as a warning before. This was already an error in dartanalyzer and DDC and will be an error in other tools in the future as well.
Added -O flag to tune optimization levels. For more details run dart2js -h -v.

We recommend to enable optimizations using the -O flag instead of individual flags for each optimization. This is because the -O flag is intended to be stable and continue to work in future versions of dart2js, while individual flags may come and go.

At this time we recommend to test and debug with -O1 and to deploy with -O3.

Tool Changes

dartfmt

Addressed several dartfmt issues when used with the new CFE parser.

Linter

Bumped the linter to 0.1.70 which includes the following new lints:

avoid_returning_null_for_void
sort_pub_dependencies
prefer_mixin
avoid_implementing_value_types
flutter_style_todos
avoid_void_async
prefer_void_to_null

and improvements:

Fixed NPE in prefer_iterable_whereType.
Improved message display for await_only_futures
Performance improvements for null_closures
Mixin support
Updated sort_constructors_first to apply to all members.
Updated unnecessary_this to work on field initializers.
Updated unawaited_futures to ignore assignments within cascades.
Improved handling of constant expressions with generic type params.
NPE fix for invariant_booleans.
Improved docs for unawaited_futures.
Updated unawaited_futures to check cascades.
Relaxed void_checks (allowing T Function() to be assigned to void Function()).
Fixed false positives in lines_longer_than_80_chars.

Pub

Renamed the --checked flag to pub run to --enable-asserts.
Pub will no longer delete directories named "packages".
The --packages-dir flag is now ignored.

2.0.0 - 2018-08-07

This is the first major version release of Dart since 1.0.0, so it contains many significant changes across all areas of the platform. Large changes include:

(Breaking) The unsound optional static type system has been replaced with a sound static type system using type inference and runtime checks. This was formerly called "strong mode" and only used by the Dart for web products. Now it is the one official static type system for the entire platform and replaces the previous "checked" and "production" modes.
(Breaking) Functions marked async now run synchronously until the first await statement. Previously, they would return to the event loop once at the top of the function body before any code runs (issue 30345).
(Breaking) Constants in the core libraries have been renamed from SCREAMING_CAPS to lowerCamelCase.
(Breaking) Many new methods have been added to core library classes. If you implement the interfaces of these classes, you will need to implement the new methods.
(Breaking) "dart:isolate" and "dart:mirrors" are no longer supported when using Dart for the web. They are still supported in the command-line VM.
(Breaking) Pub's transformer-based build system has been replaced by a new build system.
The new keyword is optional and can be omitted. Likewise, const can be omitted inside a const context (issue 30921).
Dartium is no longer maintained or supported.

Language

"Strong mode" is now the official type system of the language.
The new keyword is optional and can be omitted. Likewise, const can be omitted inside a const context.
A string in a part of declaration may now be used to refer to the library this file is part of. A library part can now declare its library as either:
```
part of name.of.library;
```
Or:
```
part of "uriReferenceOfLibrary.dart";
```
This allows libraries with no library declarations (and therefore no name) to have parts, and it allows tools to easily find the library of a part file. The Dart 1.0 syntax is supported but deprecated.
Functions marked async now run synchronously until the first await statement. Previously, they would return to the event loop once at the top of the function body before any code runs (issue 30345).
The type void is now a Top type like dynamic, and Object. It also now has new errors for being used where not allowed (such as being assigned to any non-void-typed parameter). Some libraries (importantly, mockito) may need to be updated to accept void values to keep their APIs working.
Future flattening is now done only as specified in the Dart 2.0 spec, rather than more broadly. This means that the following code has an error on the assignment to y.
```
test() {
  Future<int> f;
  var x = f.then<Future<List<int>>>((x) => []);
  Future<List<int>> y = x;
}
```

Invocations of noSuchMethod() receive default values for optional args. The following program used to print "No arguments passed", and now prints "First argument is 3".

abstract class B {
  void m([int x = 3]);
}

class A implements B {
  noSuchMethod(Invocation i) {
    if (i.positionalArguments.length == 0) {
      print("No arguments passed");
    } else {
      print("First argument is ${i.positionalArguments[0]}");
    }
  }
}

void main() {
  A().m();
}

Bounds on generic functions are invariant. The following program now issues an invalid override error (issue 29014):

class A {
  void f<T extends int>() {}
}

class B extends A {
  @override
  void f<T extends num>() {}
}

Numerous corner case bugs around return statements in synchronous and asynchronous functions fixed. Specifically:
- Issues 31887, 32881. Future flattening should not be recursive.
- Issues 30638, 32233. Incorrect downcast errors with FutureOr.
- Issue 32233. Errors when returning FutureOr.
- Issue 33218. Returns in functions with void related types.
- Issue 31278. Incorrect hint on empty returns in async. functions.
An empty return; in an async function with return type Future<Object> does not report an error.
return exp; where exp has type void in an async function is now an error unless the return type of the function is void or dynamic.
Mixed return statements of the form return; and return exp; are now allowed when exp has type void.
A compile time error is emitted for any literal which cannot be exactly represented on the target platform. As a result, dart2js and DDC report errors if an integer literal cannot be represented exactly in JavaScript (issue 33282).
New member conflict rules have been implemented. Most cases of conflicting members with the same name are now static errors (issue 33235).

Core libraries

Replaced UPPER_CASE constant names with lowerCamelCase. For example, HTML_ESCAPE is now htmlEscape.
The Web libraries were re-generated using Chrome 63 WebIDLs (details).

`dart:async`

Stream:
- Added cast and castFrom.
- Changed firstWhere, lastWhere, and singleWhere to return Future<T> and added an optional T orElse() callback.
StreamTransformer: added cast and castFrom.
StreamTransformerBase: new class.
Timer: added tick property.
Zone
- changed to be strong-mode clean. This required some breaking API changes. See https://goo.gl/y9mW2x for more information.
- Added bindBinaryCallbackGuarded, bindCallbackGuarded, and bindUnaryCallbackGuarded.
- Renamed Zone.ROOT to Zone.root.
Removed the deprecated defaultValue parameter on Stream.firstWhere and Stream.lastWhere.
Changed an internal lazily-allocated reusable "null future" to always belong to the root zone. This avoids race conditions where the first access to the future determined which zone it would belong to. The zone is only used for scheduling the callback of listeners, the listeners themselves will run in the correct zone in any case. Issue #32556.

`dart:cli`

New "provisional" library for CLI-specific features.
waitFor: function that suspends a stack to wait for a Future to complete.

`dart:collection`

MapBase: added mapToString.
LinkedHashMap no longer implements HashMap
LinkedHashSet no longer implements HashSet.
Added of constructor to Queue, ListQueue, DoubleLinkedQueue, HashSet, LinkedHashSet, SplayTreeSet, Map, HashMap, LinkedHashMap, SplayTreeMap.
Removed Maps class. Extend MapBase or mix in MapMixin instead to provide map method implementations for a class.
Removed experimental Document method getCSSCanvasContext and property supportsCssCanvasContext.
Removed obsolete Element property xtag no longer supported in browsers.
Exposed ServiceWorker class.
Added constructor to MessageChannel and MessagePort addEventListener automatically calls start method to receive queued messages.

`dart:convert`

Base64Codec.decode return type is now Uint8List.
JsonUnsupportedObjectError: added partialResult property
LineSplitter now implements StreamTransformer<String, String> instead of Converter. It retains Converter methods convert and startChunkedConversion.
Utf8Decoder when compiled with dart2js uses the browser's TextDecoder in some common cases for faster decoding.
Renamed ASCII, BASE64, BASE64URI, JSON, LATIN1 and UTF8 to ascii, base64, base64Uri, json, latin1 and utf8.
Renamed the HtmlEscapeMode constants UNKNOWN, ATTRIBUTE, SQ_ATTRIBUTE and ELEMENT to unknown, attribute, sqAttribute and elements.
Added jsonEncode, jsonDecode, base64Encode, base64UrlEncode and base64Decode top-level functions.
Changed return type of encode on AsciiCodec and Latin1Codec, and convert on AsciiEncoder, Latin1Encoder, to Uint8List.
Allow utf8.decoder.fuse(json.decoder) to ignore leading Unicode BOM.

`dart:core`

BigInt class added to support integers greater than 64-bits.
Deprecated the proxy annotation.
Added Provisional class and provisional field.
Added pragma annotation.
RegExp added static escape function.
The Uri class now correctly handles paths while running on Node.js on Windows.
Core collection changes:
- Iterable added members cast, castFrom, followedBy and whereType.
- Iterable.singleWhere added orElse parameter.
- List added + operator, first and last setters, and indexWhere and lastIndexWhere methods, and static copyRange and writeIterable methods.
- Map added fromEntries constructor.
- Map added addEntries, cast, entries, map, removeWhere, update and updateAll members.
- MapEntry: new class used by Map.entries.
- Note: if a class extends IterableBase, ListBase, SetBase or MapBase (or uses the corresponding mixins) from dart:collection, the new members are implemented automatically.
- Added of constructor to List, Set, Map.
Renamed double.INFINITY, double.NEGATIVE_INFINITY, double.NAN, double.MAX_FINITE and double.MIN_POSITIVE to double.infinity, double.negativeInfinity, double.nan, double.maxFinite and double.minPositive.
Renamed the following constants in DateTime to lower case: MONDAY through SUNDAY, DAYS_PER_WEEK (as daysPerWeek), JANUARY through DECEMBER and MONTHS_PER_YEAR (as monthsPerYear).
Renamed the following constants in Duration to lower case: MICROSECONDS_PER_MILLISECOND to microsecondsPerMillisecond, MILLISECONDS_PER_SECOND to millisecondsPerSecond, SECONDS_PER_MINUTE to secondsPerMinute, MINUTES_PER_HOUR to minutesPerHour, HOURS_PER_DAY to hoursPerDay, MICROSECONDS_PER_SECOND to microsecondsPerSecond, MICROSECONDS_PER_MINUTE to microsecondsPerMinute, MICROSECONDS_PER_HOUR to microsecondsPerHour, MICROSECONDS_PER_DAY to microsecondsPerDay, MILLISECONDS_PER_MINUTE to millisecondsPerMinute, MILLISECONDS_PER_HOUR to millisecondsPerHour, MILLISECONDS_PER_DAY to millisecondsPerDay, SECONDS_PER_HOUR to secondsPerHour, SECONDS_PER_DAY to secondsPerDay, MINUTES_PER_DAY to minutesPerDay, and ZERO to zero.
Added typeArguments to Invocation class.
Added constructors to invocation class that allows creation of Invocation objects directly, without going through noSuchMethod.
Added unaryMinus and empty constant symbols on the Symbol class.
Changed return type of UriData.dataAsBytes to Uint8List.
Added tryParse static method to int, double, num, BigInt, Uri and DateTime.
Deprecated onError parameter on int.parse, double.parse and num.parse.
Deprecated the NoSuchMethodError constructor.
int.parse on the VM no longer accepts unsigned hexadecimal numbers greater than or equal to 2**63 when not prefixed by 0x. (SDK issue 32858)

`dart:developer`

Flow class added.
Timeline.startSync and Timeline.timeSync now accepts an optional parameter flow of type Flow. The flow parameter is used to generate flow timeline events that are enclosed by the slice described by Timeline.{start,finish}Sync and Timeline.timeSync.

`dart:html`

Removed deprecated query and queryAll. Use querySelector and querySelectorAll.

`dart:io`

HttpStatus added UPGRADE_REQUIRED.
IOOverrides and HttpOverrides added to aid in writing tests that wish to mock varios dart:io objects.
Platform.operatingSystemVersion added that gives a platform-specific String describing the version of the operating system.
ProcessStartMode.INHERIT_STDIO added, which allows a child process to inherit the parent's stdio handles.
RawZLibFilter added for low-level access to compression and decompression routines.
Unified backends for SecureSocket, SecurityContext, and X509Certificate to be consistent across all platforms. All SecureSocket, SecurityContext, and X509Certificate properties and methods are now supported on iOS and OSX.
SecurityContext.alpnSupported deprecated as ALPN is now supported on all platforms.
SecurityContext: added withTrustedRoots named optional parameter constructor, which defaults to false.
Added a timeout parameter to Socket.connect, RawSocket.connect, SecureSocket.connect and RawSecureSocket.connect. If a connection attempt takes longer than the duration specified in timeout, a SocketException will be thrown. Note: if the duration specified in timeout is greater than the OS level timeout, a timeout may occur sooner than specified in timeout.
Stdin.hasTerminal added, which is true if stdin is attached to a terminal.
WebSocket added static userAgent property.
RandomAccessFile.close returns Future<void>
Added IOOverrides.socketConnect.
Added Dart-styled constants to ZLibOptions, FileMode, FileLock, FileSystemEntityType, FileSystemEvent, ProcessStartMode, ProcessSignal, InternetAddressType, InternetAddress, SocketDirection, SocketOption, RawSocketEvent, and StdioType, and deprecated the old SCREAMING_CAPS constants.
Added the Dart-styled top-level constants zlib, gzip, and systemEncoding, and deprecated the old SCREAMING_CAPS top-level constants.
Removed the top-level FileMode constants READ, WRITE, APPEND, WRITE_ONLY, and WRITE_ONLY_APPEND. Please use e.g. FileMode.read instead.
Added X509Certificate.der, X509Certificate.pem, and X509Certificate.sha1.
Added FileSystemEntity.fromRawPath constructor to allow for the creation of FileSystemEntity using Uint8List buffers.
Dart-styled constants have been added for HttpStatus, HttpHeaders, ContentType, HttpClient, WebSocketStatus, CompressionOptions, and WebSocket. The SCREAMING_CAPS constants are marked deprecated. Note that HttpStatus.CONTINUE is now HttpStatus.continue_, and that e.g. HttpHeaders.FIELD_NAME is now HttpHeaders.fieldNameHeader.
Deprecated Platform.packageRoot, which is only used for packages/ directory resolution which is no longer supported. It will now always return null, which is a value that was always possible for it to return previously.
Adds HttpClient.connectionTimeout.
Adds {Socket,RawSocket,SecureSocket}.startConnect. These return a ConnectionTask, which can be used to cancel an in-flight connection attempt.

`dart:isolate`

Make Isolate.spawn take a type parameter representing the argument type of the provided function. This allows functions with arguments types other than Object in strong mode.
Rename IMMEDIATE and BEFORE_NEXT_EVENT on Isolate to immediate and beforeNextEvent.
Deprecated Isolate.packageRoot, which is only used for packages/ directory resolution which is no longer supported. It will now always return null, which is a value that was always possible for it to return previously.
Deprecated packageRoot parameter in Isolate.spawnUri, which is was previously used only for packages/ directory resolution. That style of resolution is no longer supported in Dart 2.

`dart.math`

Renamed E, LN10, LN, LOG2E, LOG10E, PI, SQRT1_2 and SQRT2 to e, ln10, ln, log2e, log10e, pi, sqrt1_2 and sqrt2.

`dart.mirrors`

Added IsolateMirror.loadUri, which allows dynamically loading additional code.
Marked MirrorsUsed as deprecated. The MirrorsUsed annotation was only used to inform the dart2js compiler about how mirrors were used, but dart2js no longer supports the mirrors library altogether.

`dart:typed_data`

Added Unmodifiable view classes over all List types.
Renamed BYTES_PER_ELEMENT to bytesPerElement on all typed data lists.
Renamed constants XXXX through WWWW on Float32x4 and Int32x4 to lower-case xxxx through wwww.
Renamed Endinanness to Endian and its constants from BIG_ENDIAN, LITTLE_ENDIAN and HOST_ENDIAN to little, big and host.

Dart VM

Support for MIPS has been removed.
Dart int is now restricted to 64 bits. On overflow, arithmetic operations wrap around, and integer literals larger than 64 bits are not allowed. See https://github.com/dart-lang/sdk/blob/main/docs/language/informal/int64.md for details.
The Dart VM no longer attempts to perform packages/ directory resolution (for loading scripts, and in Isolate.resolveUri). Users relying on packages/ directories should switch to .packages files.

Dart for the Web

Expose JavaScript Promise APIs using Dart futures. For example, BackgroundFetchManager.get is defined as:
```
  Future<BackgroundFetchRegistration> get(String id)
```
It can be used like:
```
BackgroundFetchRegistration result = await fetchMgr.get('abc');
```
The underlying JS Promise-to-Future mechanism will be exposed as a public API in the future.

Dart Dev Compiler (DDC)

dartdevc will no longer throw an error from is checks that return a different result in weak mode (SDK issue 28988). For example:
```
main() {
  List l = [];
  // Prints "false", does not throw.
  print(l is List<String>);
}
```
Failed as casts on Iterable<T>, Map<T>, Future<T>, and Stream<T> are no longer ignored. These failures were ignored to make it easier to migrate Dart 1 code to strong mode, but ignoring them is a hole in the type system. This closes part of that hole. (We still need to stop ignoring "as" cast failures on function types, and implicit cast failures on the above types and function types.)

dart2js

dart2js now compiles programs with Dart 2.0 semantics. Apps are expected to be bigger than before, because Dart 2.0 has many more implicit checks (similar to the --checked flag in Dart 1.0).

We exposed a --omit-implicit-checks flag which removes most of the extra implicit checks. Only use this if you have enough test coverage to know that the app will work well without the checks. If a check would have failed and it is omitted, your app may crash or behave in unexpected ways. This flag is similar to --trust-type-annotations in Dart 1.0.
dart2js replaced its front-end with the common front-end (CFE). Thanks to the CFE, dart2js errors are more consistent with all other Dart tools.
dart2js replaced its source-map implementation. There aren't any big differences, but more data is emitted for synthetic code generated by the compiler.
dart:mirrors support was removed. Frameworks are encouraged to use code-generation instead. Conditional imports indicate that mirrors are not supported, and any API in the mirrors library will throw at runtime.
The generated output of dart2js can now be run as a webworker.
dart:isolate support was removed. To launch background tasks, please use webworkers instead. APIs for webworkers can be accessed from dart:html or JS-interop.
dart2js no longer supports the --package-root flag. This flag was deprecated in favor of --packages long ago.

Tool Changes

Analyzer

The analyzer will no longer issue a warning when a generic type parameter is used as the type in an instance check. For example:
```
test<T>() {
  print(3 is T); // No warning
}
```
New static checking of @visibleForTesting elements. Accessing a method, function, class, etc. annotated with @visibleForTesting from a file not in a test/ directory will result in a new hint (issue 28273).
Static analysis now respects functions annotated with @alwaysThrows (issue 31384).
New hints added:
- NULL_AWARE_BEFORE_OPERATOR when an operator is used after a null-aware access. For example:
```
x?.a - ''; // HINT
```
- NULL_AWARE_IN_LOGICAL_OPERATOR when an expression with null-aware access is used as a condition in logical operators. For example:
```
x.a || x?.b; // HINT
```
The command line analyzer (dartanalyzer) and the analysis server no longer treat directories named packages specially. Previously they had ignored these directories - and their contents - from the point of view of analysis. Now they'll be treated just as regular directories. This special-casing of packages directories was to support using symlinks for package: resolution; that functionality is now handled by .packages files.
New static checking of duplicate shown or hidden names in an export directive (issue 33182).
The analysis server will now only analyze code in Dart 2 mode ('strong mode'). It will emit warnings for analysis options files that have strong-mode: false set (and will emit a hint for strong-mode: true, which is no longer necessary).
The dartanalyzer --strong flag is now deprecated and ignored. The command-line analyzer now only analyzes code in strong mode.

dartfmt

Support assert() in const constructor initializer lists.
Better formatting for multi-line strings in argument lists.
Force splitting an empty block as the then body of an if with an else.
Support metadata annotations on enum cases.
Add --fix to remove unneeded new and const keywords, and change : to = before named parameter default values.
Change formatting rules around static methods to uniformly format code with and without new and const.
Format expressions inside string interpolation.

Pub

Pub has a brand new version solver! It supports all the same features as the old version solver, but it's much less likely to stall out on difficult package graphs, and it's much clearer about why a solution can't be found when version solving fails.
Remove support for transformers, pub build, and pub serve. Use the [new build system][transformers] instead.
There is now a default SDK constraint of <2.0.0 for any package with no existing upper bound. This allows us to move more safely to 2.0.0. All new packages published on pub will now require an upper bound SDK constraint so future major releases of Dart don't destabilize the package ecosystem.

All SDK constraint exclusive upper bounds are now treated as though they allow pre-release versions of that upper bound. For example, the SDK constraint >=1.8.0 <2.0.0 now allows pre-release SDK versions such as 2.0.0-beta.3.0. This allows early adopters to try out packages that don't explicitly declare support for the new version yet. You can disable this functionality by setting the PUB_ALLOW_PRERELEASE_SDK environment variable to false.
Allow depending on a package in a subdirectory of a Git repository. Git dependencies may now include a path parameter, indicating that the package exists in a subdirectory of the Git repository. For example:
```
dependencies:
  foobar:
    git:
      url: git://github.com/dart-lang/multi_package_repo
      path: pkg/foobar
```
Added an --executables option to pub deps command. This will list all available executables that can be run with pub run.
The Flutter sdk source will now look for packages in flutter/bin/cache/pkg/ as well as flutter/packages/. In particular, this means that packages can depend on the sky_engine package from the sdk source (issue 1775).
Pub now caches compiled packages and snapshots in the .dart_tool/pub directory, rather than the .pub directory (issue 1795).
Other bug fixes and improvements.

1.24.3 - 2017-12-14

Fix for constructing a new SecurityContext that contains the built-in certificate authority roots (issue 24693).

Core library changes

dart:io
- Unified backends for SecureSocket, SecurityContext, and X509Certificate to be consistent across all platforms. All SecureSocket, SecurityContext, and X509Certificate properties and methods are now supported on iOS and OSX.

1.24.2 - 2017-06-22

Fixes for debugging in Dartium.
- Fix DevConsole crash with JS (issue 29873).
- Fix debugging in WebStorm, NULL returned for JS objects (issue 29854).

1.24.1 - 2017-06-14

Bug fixes for dartdevc support in pub serve.
- Fixed module config invalidation logic so modules are properly recalculated when package layout changes.
- Fixed exception when handling require.js errors that aren't script load errors.
- Fixed an issue where requesting the bootstrap.js file before the dart.js file would result in a 404.
- Fixed a Safari issue during bootstrapping (note that Safari is still not officially supported but does work for trivial examples).
Fix for a Dartium issue where there was no sound in checked mode (issue 29810).

1.24.0 - 2017-06-12

Language

During a dynamic type check, void is not required to be null anymore. In practice, this makes overriding void functions with non-void functions safer.
During static analysis, a function or setter declared using => with return type void now allows the returned expression to have any type. For example, assuming the declaration int x;, it is now type correct to have void f() => ++x;.
A new function-type syntax has been added to the language. Warning: In Dart 1.24, this feature is incomplete, and not stable in the Analyzer.

Intuitively, the type of a function can be constructed by textually replacing the function's name with Function in its declaration. For instance, the type of void foo() {} would be void Function(). The new syntax may be used wherever a type can be written. It is thus now possible to declare fields containing functions without needing to write typedefs: void Function() x;. The new function type has one restriction: it may not contain the old-style function-type syntax for its parameters. The following is thus illegal: void Function(int f()). typedefs have been updated to support this new syntax.

Examples:
```
typedef F = void Function();  // F is the name for a `void` callback.
int Function(int) f;  // A field `f` that contains an int->int function.

class A<T> {
  // The parameter `callback` is a function that takes a `T` and returns
  // `void`.
  void forEach(void Function(T) callback);
}

// The new function type supports generic arguments.
typedef Invoker = T Function<T>(T Function() callback);
```

Core library changes

dart:async, dart:core, dart:io
- Adding to a closed sink, including IOSink, is no longer not allowed. In 1.24, violations are only reported (on stdout or stderr), but a future version of the Dart SDK will change this to throwing a StateError.
dart:convert
- BREAKING Removed the deprecated ChunkedConverter class.
- JSON maps are now typed as Map<String, dynamic> instead of Map<dynamic, dynamic>. A JSON-map is not a HashMap or LinkedHashMap anymore (but just a Map).
dart:io
- Added Platform.localeName, needed for accessing the locale on platforms that don't store it in an environment variable.
- Added ProcessInfo.currentRss and ProcessInfo.maxRss for inspecting the Dart VM process current and peak resident set size.
- Added RawSynchronousSocket, a basic synchronous socket implementation.
dart: web APIs have been updated to align with Chrome v50. This change includes a large number of changes, many of which are breaking. In some cases, new class names may conflict with names that exist in existing code.
dart:html
- REMOVED classes: Bluetooth, BluetoothDevice, BluetoothGattCharacteristic, BluetoothGattRemoteServer, BluetoothGattService, BluetoothUuid, CrossOriginConnectEvent, DefaultSessionStartEvent, DomSettableTokenList, MediaKeyError, PeriodicSyncEvent, PluginPlaceholderElement, ReadableStream, StashedMessagePort, SyncRegistration
- REMOVED members:
  - texImage2DCanvas was removed from RenderingContext.
  - endClip and startClip were removed from Animation.
  - after and before were removed from CharacterData, ChildNode and Element.
  - keyLocation was removed from KeyboardEvent. Use location instead.
  - generateKeyRequest, keyAddedEvent, keyErrorEvent, keyMessageEvent, mediaGroup, needKeyEvent, onKeyAdded, onKeyError, onKeyMessage, and onNeedKey were removed from MediaElement.
  - getStorageUpdates was removed from Navigator
  - status was removed from PermissionStatus
  - getAvailability was removed from PreElement
- Other behavior changes:
  - URLs returned in CSS or html are formatted with quoted string. Like url("http://google.com") instead of url(http://google.com).
  - Event timestamp property type changed from int to num.
  - Chrome introduced slight layout changes of UI objects. In addition many height/width dimensions are returned in subpixel values (num instead of whole numbers).
  - setRangeText with a selectionMode value of 'invalid' is no longer valid. Only "select", "start", "end", "preserve" are allowed.
dart:svg
- A large number of additions and removals. Review your use of dart:svg carefully.
dart:web_audio
- new method on AudioContext - createIirFilter returns a new class IirFilterNode.
dart:web_gl
- new classes: CompressedTextureAstc, ExtColorBufferFloat, ExtDisjointTimerQuery, and TimerQueryExt.
- ExtFragDepth added: readPixels2 and texImage2D2.

Strong Mode

Removed ad hoc Future.then inference in favor of using FutureOr. Prior to adding FutureOr to the language, the analyzer implemented an ad hoc type inference for Future.then (and overrides) treating it as if the onValue callback was typed to return FutureOr for the purposes of inference. This ad hoc inference has been removed now that FutureOr has been added.

Packages that implement Future must either type the onValue parameter to .then as returning FutureOr<T>, or else must leave the type of the parameter entirely to allow inference to fill in the type.
During static analysis, a function or setter declared using => with return type void now allows the returned expression to have any type.

Tool Changes

Dartium

Dartium is now based on Chrome v50. See Core library changes above for details on the changed APIs.
Pub
- pub build and pub serve
  - Added support for the Dart Development Compiler.
    
    Unlike dart2js, this new compiler is modular, which allows pub to do incremental re-builds for pub serve, and potentially pub build in the future.
    
    In practice what that means is you can edit your Dart files, refresh in Chrome (or other supported browsers), and see your edits almost immediately. This is because pub is only recompiling your package, not all packages that you depend on.
    
    There is one caveat with the new compiler, which is that your package and your dependencies must all be strong mode clean. If you are getting an error compiling one of your dependencies, you will need to file bugs or send pull requests to get them strong mode clean.
    
    There are two ways of opting into the new compiler:
    - Use the new --web-compiler flag, which supports dartdevc, dart2js or none as options. This is the easiest way to try things out without changing the default.
    - Add config to your pubspec. There is a new web key which supports a single key called compiler. This is a map from mode names to compiler to use. For example, to default to dartdevc in debug mode you can add the following to your pubspec:
      web: compiler: debug: dartdevc
    You can also use the new compiler to run your tests in Chrome much more quickly than you can with dart2js. In order to do that, run pub serve test --web-compiler=dartdevc, and then run pub run test -p chrome --pub-serve=8080.
  - The --no-dart2js flag has been deprecated in favor of --web-compiler=none.
  - pub build will use a failing exit code if there are errors in any transformer.
- pub publish
  - Added support for the UNLICENSE file.
  - Packages that depend on the Flutter SDK may be published.
- pub get and pub upgrade
  - Don't dump a stack trace when a network error occurs while fetching packages.
dartfmt
- Preserve type parameters in new generic function typedef syntax.
- Add self-test validation to ensure formatter bugs do not cause user code to be lost.

Infrastructure changes

As of this release, we'll show a warning when using the MIPS architecture. Unless we learn about any critical use of Dart on MIPS in the meantime, we're planning to deprecate support for MIPS starting with the next stable release.

1.23.0 - 2017-04-21

Strong Mode

Breaking change - it is now a strong mode error if a mixin causes a name conflict between two private members (field/getter/setter/method) from a different library. (SDK issue 28809).

lib1.dart:

class A {
  int _x;
}

class B {
  int _x;
}

lib2.dart:

import 'lib1.dart';

class C extends A with B {}

    error • The private name _x, defined by B, conflicts with the same name defined by A at tmp/lib2.dart:3:24 • private_collision_in_mixin_application

Breaking change - strong mode will prefer the expected type to infer generic types, functions, and methods (SDK issue 27586).

main() {
  List<Object> foo = /*infers: <Object>*/['hello', 'world'];
  var bar = /*infers: <String>*/['hello', 'world'];
}

Strong mode inference error messages are improved (SDK issue 29108).

import 'dart:math';
test(Iterable/* fix is to add <num> here */ values) {
  num n = values.fold(values.first as num, max);
}

Now produces the error on the generic function "max":

Couldn't infer type parameter 'T'.

Tried to infer 'dynamic' for 'T' which doesn't work:
  Function type declared as '<T extends num>(T, T) → T'
                used where  '(num, dynamic) → num' is required.

Consider passing explicit type argument(s) to the generic.

Strong mode supports overriding fields, @virtual is no longer required (SDK issue 28120).

class C {
  int x = 42;
}
class D extends C {
  get x {
    print("x got called");
    return super.x;
  }
}
main() {
  print(new D().x);
}

Strong mode down cast composite warnings are no longer issued by default. (SDK issue 28588).

void test() {
  List untyped = [];
  List<int> typed = untyped; // No down cast composite warning
}

To opt back into the warnings, add the following to the .analysis_options file for your project.

analyzer:
  errors:
    strong_mode_down_cast_composite: warning

Core library changes

dart:core
- Added Uri.isScheme function to check the scheme of a URI. Example: uri.isScheme("http"). Ignores case when comparing.
- Make UriData.parse validate its input better. If the data is base-64 encoded, the data is normalized wrt. alphabet and padding, and it contains invalid base-64 data, parsing fails. Also normalizes non-base-64 data.
dart:io
- Added functions File.lastAccessed, File.lastAccessedSync, File.setLastModified, File.setLastModifiedSync, File.setLastAccessed, and File.setLastAccessedSync.
- Added {Stdin,Stdout}.supportsAnsiEscapes.

Dart VM

Calls to print() and Stdout.write*() now correctly print unicode characters to the console on Windows. Calls to Stdout.add*() behave as before.

Tool changes

Analysis
- dartanalyzer now follows the same rules as the analysis server to find an analysis options file, stopping when an analysis options file is found:
  - Search up the directory hierarchy looking for an analysis options file.
  - If analyzing a project referencing the Flutter package, then use the default Flutter analysis options found in package:flutter.
  - If in a Bazel workspace, then use the analysis options in package:dart.analysis_options/default.yaml if it exists.
  - Use the default analysis options rules.
- In addition, specific to dartanalyzer:
  - an analysis options file can be specified on the command line via --options and that file will be used instead of searching for an analysis options file.
  - any analysis option specified on the command line (e.g. --strong or --no-strong) takes precedence over any corresponding value specified in the analysis options file.
Dartium, dart2js, and DDC
- Imports to dart:io are allowed, but the imported library is not supported and will likely fail on most APIs at runtime. This change was made as a stopgap measure to make it easier to write libraries that share code between platforms (like package http). This might change again when configuration specific imports are supported.
Pub
- Now sends telemetry data to pub.dartlang.org to allow better understanding of why a particular package is being accessed.
- pub publish
  - Warns if a package imports a package that's not a dependency from within lib/ or bin/, or a package that's not a dev dependency from within benchmark/, example/, test/ or tool/.
  - No longer produces "UID too large" errors on OS X. All packages are now uploaded with the user and group names set to "pub".
  - No longer fails with a stack overflow when uploading a package that uses Git submodules.
- pub get and pub upgrade
  - Produce more informative error messages if they're run directly in a package that uses Flutter.
  - Properly unlock SDK and path dependencies if they have a new version that's also valid according to the user's pubspec.
dartfmt
- Support new generic function typedef syntax.
- Make the precedence of cascades more visible.
- Fix a couple of places where spurious newlines were inserted.
- Correctly report unchanged formatting when reading from stdin.
- Ensure space between - and --. Code that does this is pathological, but it technically meant dartfmt could change the semantics of the code.
- Preserve a blank line between enum cases.
- Other small formatting tweaks.

1.22.1 - 2017-02-22

Patch release, resolves two issues:

Dart VM crash: Issue 28072
Dart VM bug combining types, await, and deferred loading: Issue 28678

1.22.0 - 2017-02-14

Language

Breaking change: 'Generalized tear-offs' are no longer supported, and will cause errors. We updated the language spec and added warnings in 1.21, and are now taking the last step to fully de-support them. They were previously only supported in the VM, and there are almost no known uses of them in the wild.

The assert() statement has been expanded to support an optional second message argument (SDK issue 27342).

The message is displayed if the assert fails. It can be any object, and it is accessible as AssertionError.message. It can be used to provide more user friendly exception outputs. As an example, the following assert:

assert(configFile != null, "Tool config missing. Please see https://goo.gl/k8iAi for details.");

would produce the following exception output:

Unhandled exception:
'file:///Users/mit/tmp/tool/bin/main.dart': Failed assertion: line 9 pos 10:
'configFile != null': Tool config missing. Please see https://goo.gl/k8iAi for details.
#0      _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:33)
#1      _AssertionError._throwNew (dart:core-patch/errors_patch.dart:29)
#2      main (file:///Users/mit/tmp/tool/bin/main.dart:9:10)

The Null type has been moved to the bottom of the type hierarchy. As such, it is considered a subtype of every other type. The null literal was always treated as a bottom type. Now the named class Null is too:

const empty = <Null>[];

String concatenate(List<String> parts) => parts.join();
int sum(List<int> numbers) => numbers.fold(0, (sum, n) => sum + n);

concatenate(empty); // OK.
sum(empty); // OK.

Introduce covariant modifier on parameters. It indicates that the parameter (and the corresponding parameter in any method that overrides it) has looser override rules. In strong mode, these require a runtime type check to maintain soundness, but enable an architectural pattern that is useful in some code.

It lets you specialize a family of classes together, like so:
```
abstract class Predator {
  void chaseAndEat(covariant Prey p);
}

abstract class Prey {}

class Mouse extends Prey {}

class Seal extends Prey {}

class Cat extends Predator {
  void chaseAndEat(Mouse m) => ...
}

class Orca extends Predator {
  void chaseAndEat(Seal s) => ...
}
```
This isn't statically safe, because you could do:
```
Predator predator = new Cat(); // Upcast.
predator.chaseAndEat(new Seal()); // Cats can't eat seals!
```
To preserve soundness in strong mode, in the body of a method that uses a covariant override (here, Cat.chaseAndEat()), the compiler automatically inserts a check that the parameter is of the expected type. So the compiler gives you something like:
```
class Cat extends Predator {
  void chaseAndEat(o) {
    var m = o as Mouse;
    ...
  }
}
```
Spec mode allows this unsound behavior on all parameters, even though users rarely rely on it. Strong mode disallowed it initially. Now, strong mode lets you opt into this behavior in the places where you do want it by using this modifier. Outside of strong mode, the modifier is ignored.
Change instantiate-to-bounds rules for generic type parameters when running in strong mode. If you leave off the type parameters from a generic type, we need to decide what to fill them in with. Dart 1.0 says just use dynamic, but that isn't sound:
```
class Abser<T extends num> {
   void absThis(T n) { n.abs(); }
}

var a = new Abser(); // Abser<dynamic>.
a.absThis("not a num");
```
We want the body of absThis() to be able to safely assume n is at least a num -- that's why there's a constraint on T, after all. Implicitly using dynamic as the type parameter in this example breaks that.

Instead, strong mode uses the bound. In the above example, it fills it in with num, and then the second line where a string is passed becomes a static error.

However, there are some cases where it is hard to figure out what that default bound should be:
```
class RuhRoh<T extends Comparable<T>> {}
```
Strong mode's initial behavior sometimes produced surprising, unintended results. For 1.22, we take a simpler approach and then report an error if a good default type argument can't be found.

Core libraries

Define FutureOr<T> for code that works with either a future or an immediate value of some type. For example, say you do a lot of text manipulation, and you want a handy function to chain a bunch of them:
```
typedef String StringSwizzler(String input);

String swizzle(String input, List<StringSwizzler> swizzlers) {
  var result = input;
  for (var swizzler in swizzlers) {
    result = swizzler(result);
  }

  return result;
}
```
This works fine:
```
main() {
  var result = swizzle("input", [
    (s) => s.toUpperCase(),
    (s) => () => s * 2)
  ]);
  print(result); // "INPUTINPUT".
}
```
Later, you realize you'd also like to support swizzlers that are asynchronous (maybe they look up synonyms for words online). You could make your API strictly asynchronous, but then users of simple synchronous swizzlers have to manually wrap the return value in a Future.value(). Ideally, your swizzle() function would be "polymorphic over asynchrony". It would allow both synchronous and asynchronous swizzlers. Because await accepts immediate values, it is easy to implement this dynamically:
```
Future<String> swizzle(String input, List<StringSwizzler> swizzlers) async {
  var result = input;
  for (var swizzler in swizzlers) {
    result = await swizzler(result);
  }

  return result;
}

main() async {
  var result = swizzle("input", [
    (s) => s.toUpperCase(),
    (s) => new Future.delayed(new Duration(milliseconds: 40), () => s * 2)
  ]);
  print(await result);
}
```
What should the declared return type on StringSwizzler be? In the past, you had to use dynamic or Object, but that doesn't tell the user much. Now, you can do:
```
typedef FutureOr<String> StringSwizzler(String input);
```
Like the name implies, FutureOr<String> is a union type. It can be a String or a Future<String>, but not anything else. In this case, that's not super useful beyond just stating a more precise type for readers of the code. It does give you a little better error checking in code that uses the result of that.

FutureOr<T> becomes really important in generic methods like Future.then(). In those cases, having the type system understand this magical union type helps type inference figure out the type argument of then() based on the closure you pass it.

Previously, strong mode had hard-coded rules for handling Future.then() specifically. FutureOr<T> exposes that functionality so third-party APIs can take advantage of it too.

Tool changes

Dart2Js
- Remove support for (long-time deprecated) mixin typedefs.
Pub
- Avoid using a barback asset server for executables unless they actually use transformers. This makes precompilation substantially faster, produces better error messages when precompilation fails, and allows globally-activated executables to consistently use the Isolate.resolvePackageUri() API.
- On Linux systems, always ignore packages' original file owners and permissions when extracting those packages. This was already the default under most circumstances.
- Properly close the standard input stream of child processes started using pub run.
- Handle parse errors from the package cache more gracefully. A package whose pubspec can't be parsed will now be ignored by pub get --offline and deleted by pub cache repair.
- Make pub run run executables in spawned isolates. This lets them handle signals and use standard IO reliably.
- Fix source-maps produced by dart2js when running in pub serve: URL references to assets from packages match the location where pub serve serves them (packages/package_name/ instead of ../packages/package_name/).

Infrastructure changes

The SDK now uses GN rather than gyp to generate its build files, which will now be exclusively ninja flavored. Documentation can be found on our wiki. Also see the help message of tools/gn.py. This change is in response to the deprecation of gyp. Build file generation with gyp will continue to be available in this release by setting the environment variable DART_USE_GYP before running gclient sync or gclient runhooks, but this will be removed in a future release.

1.21.1 - 2017-01-13

Patch release, resolves one issue:

Dart VM: Snapshots of generic functions fail. Issue 28072

1.21.0 - 2016-12-07

Language

Support generic method syntax. Type arguments are not available at runtime. For details, check the informal specification.
Support access to initializing formals, e.g., the use of x to initialize y in class C { var x, y; C(this.x): y = x; }. Please check the informal specification for details.
Don't warn about switch case fallthrough if the case ends in a rethrow statement. (SDK issue 27650)
Also don't warn if the entire switch case is wrapped in braces - as long as the block ends with a break, continue, rethrow, return or throw.
Allow = as well as : as separator for named parameter default values.
```
enableFlags({bool hidden: false}) { … }
```
can now be replaced by
```
enableFlags({bool hidden = false}) { … }
```
(SDK issue 27559)

Core library changes

dart:core: Set.difference now takes a Set<Object> as argument. (SDK issue 27573)
dart:developer
- Added Service class.
  - Allows inspecting and controlling the VM service protocol HTTP server.
  - Provides an API to access the ID of an Isolate.

Tool changes

Dart Dev Compiler
- Support calls to loadLibrary() on deferred libraries. Deferred libraries are still loaded eagerly. (SDK issue 27343)

1.20.1 - 2016-10-13

Patch release, resolves one issue:

Dartium: Fixes a bug that caused crashes. No issue filed.

Strong Mode

It is no longer a warning when casting from dynamic to a composite type (SDK issue 27766).

main() {
  dynamic obj = <int>[1, 2, 3];
  // This is now allowed without a warning.
  List<int> list = obj;
}

1.20.0 - 2016-10-11

Dart VM

We have improved the way that the VM locates the native code library for a native extension (e.g. dart-ext: import). We have updated this article on native extensions to reflect the VM's improved behavior.
Linux builds of the VM will now use the tcmalloc library for memory allocation. This has the advantages of better debugging and profiling support and faster small allocations, with the cost of slightly larger initial memory footprint, and slightly slower large allocations.
We have improved the way the VM searches for trusted root certificates for secure socket connections on Linux. First, the VM will look for trusted root certificates in standard locations on the file system (/etc/pki/tls/certs/ca-bundle.crt followed by /etc/ssl/certs), and only if these do not exist will it fall back on the builtin trusted root certificates. This behavior can be overridden on Linux with the new flags --root-certs-file and --root-certs-cache. The former is the path to a file containing the trusted root certificates, and the latter is the path to a directory containing root certificate files hashed using c_rehash.
The VM now throws a catchable Error when method compilation fails. This allows easier debugging of syntax errors, especially when testing. (SDK issue 23684)

Core library changes

dart:core: Remove deprecated Resource class. Use the class in package:resource instead.
dart:async
- Future.wait now catches synchronous errors and returns them in the returned Future. (SDK issue 27249)
- More aggressively returns a Future on Stream.cancel operations. Discourages to return null from cancel. (SDK issue 26777)
- Fixes a few bugs where the cancel future wasn't passed through transformations.
dart:io
- Added WebSocket.addUtf8Text to allow sending a pre-encoded text message without a round-trip UTF-8 conversion. (SDK issue 27129)

Strong Mode

Breaking change - it is an error if a generic type parameter cannot be inferred (SDK issue 26992).

class Cup<T> {
  Cup(T t);
}
main() {
  // Error because:
  // - if we choose Cup<num> it is not assignable to `cOfInt`,
  // - if we choose Cup<int> then `n` is not assignable to int.
  num n;
  C<int> cOfInt = new C(n);
}

New feature - use @checked to override a method and tighten a parameter type (SDK issue 25578).

import 'package:meta/meta.dart' show checked;
class View {
  addChild(View v) {}
}
class MyView extends View {
  // this override is legal, it will check at runtime if we actually
  // got a MyView.
  addChild(@checked MyView v) {}
}
main() {
  dynamic mv = new MyView();
  mv.addChild(new View()); // runtime error
}

New feature - use @virtual to allow field overrides in strong mode (SDK issue 27384).

import 'package:meta/meta.dart' show virtual;
class Base {
  @virtual int x;
}
class Derived extends Base {
  int x;

  // Expose the hidden storage slot:
  int get superX => super.x;
  set superX(int v) { super.x = v; }
}

Breaking change - infer list and map literals from the context type as well as their values, consistent with generic methods and instance creation (SDK issue 27151).

import 'dart:async';
main() async {
  var b = new Future<B>.value(new B());
  var c = new Future<C>.value(new C());
  var/*infer List<Future<A>>*/ list = [b, c];
  var/*infer List<A>*/ result = await Future.wait(list);
}
class A {}
class B extends A {}
class C extends A {}

Tool changes

dartfmt - upgraded to v0.2.10
- Don't crash on annotations before parameters with trailing commas.
- Always split enum declarations if they end in a trailing comma.
- Add --set-exit-if-changed to set the exit code on a change.
Pub
- Pub no longer generates a packages/ directory by default. Instead, it generates a .packages file, called a package spec. To generate a packages/ directory in addition to the package spec, use the --packages-dir flag with pub get, pub upgrade, and pub downgrade. See the Good-bye symlinks article for details.

1.19.1 - 2016-09-08

Patch release, resolves one issue:

Dartdoc: Fixes a bug that prevented generation of docs. (Dartdoc issue 1233)

1.19.0 - 2016-08-26

Language changes

The language now allows a trailing comma after the last argument of a call and the last parameter of a function declaration. This can make long argument or parameter lists easier to maintain, as commas can be left as-is when reordering lines. For details, see SDK issue 26644.

Tool Changes

dartfmt - upgraded to v0.2.9+1
- Support trailing commas in argument and parameter lists.
- Gracefully handle read-only files.
- About a dozen other bug fixes.
Pub
- Added a --no-packages-dir flag to pub get, pub upgrade, and pub downgrade. When this flag is passed, pub will not generate a packages/ directory, and will remove that directory and any symlinks to it if they exist. Note that this replaces the unsupported --no-package-symlinks flag.
- Added the ability for packages to declare a constraint on the Flutter SDK:
```
environment:
  flutter: ^0.1.2
  sdk: >=1.19.0 <2.0.0
```
  A Flutter constraint will only be satisfiable when pub is running in the context of the flutter executable, and when the Flutter SDK version matches the constraint.
- Added sdk as a new package source that fetches packages from a hard-coded SDK. Currently only the flutter SDK is supported:
```
dependencies:
  flutter_driver:
    sdk: flutter
    version: ^0.0.1
```
  A Flutter sdk dependency will only be satisfiable when pub is running in the context of the flutter executable, and when the Flutter SDK contains a package with the given name whose version matches the constraint.
- tar files on Linux are now created with 0 as the user and group IDs. This fixes a crash when publishing packages while using Active Directory.
- Fixed a bug where packages from a hosted HTTP URL were considered the same as packages from an otherwise-identical HTTPS URL.
- Fixed timer formatting for timers that lasted longer than a minute.
- Eliminate some false negatives when determining whether global executables are on the user's executable path.
dart2js
- dart2dart (aka dart2js --output-type=dart) has been removed (this was deprecated in Dart 1.11).

Dart VM

The dependency on BoringSSL has been rolled forward. Going forward, builds of the Dart VM including secure sockets will require a compiler with C++11 support. For details, see the Building wiki page.

Strong Mode

New feature - an option to disable implicit casts (SDK issue 26583), see the documentation for usage instructions and examples.
New feature - an option to disable implicit dynamic (SDK issue 25573), see the documentation for usage instructions and examples.

Breaking change - infer generic type arguments from the constructor invocation arguments (SDK issue 25220).

var map = new Map<String, String>();

// infer: Map<String, String>
var otherMap = new Map.from(map);

Breaking change - infer local function return type (SDK issue 26414).

void main() {
  // infer: return type is int
  f() { return 40; }
  int y = f() + 2; // type checks
  print(y);
}

Breaking change - allow type promotion from a generic type parameter (SDK issue 26414).

void fn/*<T>*/(/*=T*/ object) {
  if (object is String) {
    // Treat `object` as `String` inside this block.
    // But it will require a cast to pass it to something that expects `T`.
    print(object.substring(1));
  }
}

Breaking change - smarter inference for Future.then (SDK issue 25944). Previous workarounds that use async/await or .then/*<Future<SomeType>>*/ should no longer be necessary.
```
// This will now infer correctly.
Future<List<int>> t2 = f.then((_) => [3]);
// This infers too.
Future<int> t2 = f.then((_) => new Future.value(42));
```

Breaking change - smarter inference for async functions (SDK issue 25322).

void test() async {
  List<int> x = await [4]; // was previously inferred
  List<int> y = await new Future.value([4]); // now inferred too
}

Breaking change - sideways casts are no longer allowed (SDK issue 26120).

1.18.1 - 2016-08-02

Patch release, resolves two issues and improves performance:

Debugger: Fixes a bug that crashes the VM (SDK issue 26941)
VM: Fixes an optimizer bug involving closures, try, and await (SDK issue 26948)
Dart2js: Speeds up generated code on Firefox (https://codereview.chromium.org/2180533002)

1.18.0 - 2016-07-27

Core library changes

dart:core
- Improved performance when parsing some common URIs.
- Fixed bug in Uri.resolve (SDK issue 26804).
dart:io
- Adds file locking modes FileLock.BLOCKING_SHARED and FileLock.BLOCKING_EXCLUSIVE.

1.17.1 - 2016-06-10

Patch release, resolves two issues:

VM: Fixes a bug that caused crashes in async functions. (SDK issue 26668)
VM: Fixes a bug that caused garbage collection of reachable weak properties. (https://codereview.chromium.org/2041413005)

1.17.0 - 2016-06-08

Core library changes

dart:convert
- Deprecate ChunkedConverter which was erroneously added in 1.16.
dart:core
- Uri.replace supports iterables as values for the query parameters.
- Uri.parseIPv6Address returns a Uint8List.
dart:io
- Added NetworkInterface.listSupported, which is true when NetworkInterface.list is supported, and false otherwise. Currently, NetworkInterface.list is not supported on Android.

Tool Changes

Pub
- TAR files created while publishing a package on Mac OS and Linux now use a more portable format.
- Errors caused by invalid arguments now print the full usage information for the command.
- SDK constraints for dependency overrides are no longer considered when determining the total SDK constraint for a lockfile.
- A bug has been fixed in which a lockfile was considered up-to-date when it actually wasn't.
- A bug has been fixed in which pub get --offline would crash when a prerelease version was selected.
Dartium and content shell
- Debugging Dart code inside iframes improved, was broken.

1.16.1 - 2016-05-24

Patch release, resolves one issue:

VM: Fixes a bug that caused intermittent hangs on Windows. (SDK issue 26400)

1.16.0 - 2016-04-26

Core library changes

dart:convert
- Added BASE64URL codec and corresponding Base64Codec.urlSafe constructor.
- Introduce ChunkedConverter and deprecate chunked methods on Converter.
dart:html

There have been a number of BREAKING changes to align APIs with recent changes in Chrome. These include:
- Chrome's ShadowRoot interface no longer has the methods getElementById, getElementsByClassName, and getElementsByTagName, e.g.,
```
elem.shadowRoot.getElementsByClassName('clazz')
```
  should become:
```
elem.shadowRoot.querySelectorAll('.clazz')
```
- The clipboardData property has been removed from KeyEvent and Event. It has been moved to the new ClipboardEvent class, which is now used by copy, cut, and paste events.
- The layer property has been removed from KeyEvent and UIEvent. It has been moved to MouseEvent.
- The Point get page property has been removed from UIEvent. It still exists on MouseEvent and Touch.
There have also been a number of other additions and removals to dart:html, dart:indexed_db, dart:svg, dart:web_audio, and dart:web_gl that correspond to changes to Chrome APIs between v39 and v45. Many of the breaking changes represent APIs that would have caused runtime exceptions when compiled to JavaScript and run on recent Chrome releases.
dart:io
- Added SecurityContext.alpnSupported, which is true if a platform supports ALPN, and false otherwise.

JavaScript interop

For performance reasons, a potentially BREAKING change was added for libraries that use JS interop. Any Dart file that uses @JS annotations on declarations (top-level functions, classes or class members) to interop with JavaScript code will require that the file have the annotation @JS() on a library directive.

@JS()
library my_library;

The analyzer will enforce this by generating the error:

The @JS() annotation can only be used if it is also declared on the library directive.

If part file uses the @JS() annotation, the library that uses the part should have the @JS() annotation e.g.,

// library_1.dart
@JS()
library library_1;

import 'package:js/js.dart';

part 'part_1.dart';

// part_1.dart
part of library_1;

@JS("frameworkStabilizers")
external List<FrameworkStabilizer> get frameworkStabilizers;

If your library already has a JS module e.g.,

@JS('array.utils')
library my_library;

Then your library will work without any additional changes.

Analyzer

Static checking of for in statements. These will now produce static warnings:

// Not Iterable.
for (var i in 1234) { ... }

// String cannot be assigned to int.
for (int n in <String>["a", "b"]) { ... }

Tool Changes

Pub
- pub serve now provides caching headers that should improve the performance of requesting large files multiple times.
- Both pub get and pub upgrade now have a --no-precompile flag that disables precompilation of executables and transformed dependencies.
- pub publish now resolves symlinks when publishing from a Git repository. This matches the behavior it always had when publishing a package that wasn't in a Git repository.
Dart Dev Compiler
- The experimental dartdevc executable has been added to the SDK.
- It will help early adopters validate the implementation and provide feedback. dartdevc is not yet ready for production usage.
- Read more about the Dart Dev Compiler here.

1.15.0 - 2016-03-09

Core library changes

dart:async
- Made StreamView class a const class.
dart:core
- Added Uri.queryParametersAll to handle multiple query parameters with the same name.
dart:io
- Added SecurityContext.usePrivateKeyBytes, SecurityContext.useCertificateChainBytes, SecurityContext.setTrustedCertificatesBytes, and SecurityContext.setClientAuthoritiesBytes.
- Breaking The named directory argument of SecurityContext.setTrustedCertificates has been removed.
- Added support to SecurityContext for PKCS12 certificate and key containers.
- All calls in SecurityContext that accept certificate data now accept an optional named parameter password, similar to SecurityContext.usePrivateKeyBytes, for use as the password for PKCS12 data.

Tool changes

Dartium and content shell
- The Chrome-based tools that ship as part of the Dart SDK - Dartium and content shell - are now based on Chrome version 45 (instead of Chrome 39).
- Dart browser libraries (dart:html, dart:svg, etc) have not been updated.
  - These are still based on Chrome 39.
  - These APIs will be updated in a future release.
- Note that there are experimental APIs which have changed in the underlying browser, and will not work with the older libraries. For example, Element.animate.
dartfmt - upgraded to v0.2.4
- Better handling for long collections with comments.
- Always put member metadata annotations on their own line.
- Indent functions in named argument lists with non-functions.
- Force the parameter list to split if a split occurs inside a function-typed parameter.
- Don't force a split for before a single named argument if the argument itself splits.

Service protocol changes

Fixed a documentation bug where the field extensionRPCs in Isolate was not marked optional.

Experimental language features

Added support for configuration-specific imports. On the VM and dart2js, they can be enabled with --conditional-directives.

The analyzer requires additional configuration:
```
analyzer:
  language:
    enableConditionalDirectives: true
```
Read about configuring the analyzer for more details.

1.14.2 - 2016-02-10

Patch release, resolves three issues:

VM: Fixed a code generation bug on x64. (SDK commit 834b3f02)
dart:io: Fixed EOF detection when reading some special device files. (SDK issue 25596)
Pub: Fixed an error using hosted dependencies in SDK version 1.14. (Pub issue 1386)

1.14.1 - 2016-02-04

Patch release, resolves one issue:

Debugger: Fixes a VM crash when a debugger attempts to set a break point during isolate initialization. (SDK issue 25618)

1.14.0 - 2016-01-28

Core library changes

dart:async
- Added Future.any static method.
- Added Stream.fromFutures constructor.
dart:convert
- Base64Decoder.convert now takes optional start and end parameters.
dart:core
- Added current getter to StackTrace class.
- Uri class added support for data URIs
  - Added two new constructors: dataFromBytes and dataFromString.
  - Added a data getter for data: URIs with a new UriData class for the return type.
- Added growable parameter to List.filled constructor.
- Added microsecond support to DateTime: DateTime.microsecond, DateTime.microsecondsSinceEpoch, and new DateTime.fromMicrosecondsSinceEpoch.
dart:math
- Random added a secure constructor returning a cryptographically secure random generator which reads from the entropy source provided by the embedder for every generated random value.
dart:io
- Platform added a static isIOS getter and Platform.operatingSystem may now return ios.
- Platform added a static packageConfig getter.
- Added support for WebSocket compression as standardized in RFC 7692.
- Compression is enabled by default for all WebSocket connections.
  - The optionally named parameter compression on the methods WebSocket.connect, WebSocket.fromUpgradedSocket, and WebSocketTransformer.upgrade and the WebSocketTransformer constructor can be used to modify or disable compression using the new CompressionOptions class.
dart:isolate
- Added experimental support for Package Resolution Configuration.
  - Added packageConfig and packageRoot instance getters to Isolate.
  - Added a resolvePackageUri method to Isolate.
  - Added named arguments packageConfig and automaticPackageResolution to the Isolate.spawnUri constructor.

Tool changes

dartfmt
- Better line splitting in a variety of cases.
- Other optimizations and bug fixes.
Pub
- Breaking: Pub now eagerly emits an error when a pubspec's "name" field is not a valid Dart identifier. Since packages with non-identifier names were never allowed to be published, and some of them already caused crashes when being written to a .packages file, this is unlikely to break many people in practice.
- Breaking: Support for barback versions prior to 0.15.0 (released July
  1. has been dropped. Pub will no longer install these older barback versions.
- pub serve now GZIPs the assets it serves to make load times more similar to real-world use-cases.
- pub deps now supports a --no-dev flag, which causes it to emit the dependency tree as it would be if no dev_dependencies were in use. This makes it easier to see your package's dependency footprint as your users will experience it.
- pub global run now detects when a global executable's SDK constraint is no longer met and errors out, rather than trying to run the executable anyway.
- Pub commands that check whether the lockfile is up-to-date (pub run, pub deps, pub serve, and pub build) now do additional verification. They ensure that any path dependencies' pubspecs haven't been changed, and they ensure that the current SDK version is compatible with all dependencies.
- Fixed a crashing bug when using pub global run on a global script that didn't exist.
- Fixed a crashing bug when a pubspec contains a dependency without a source declared.

1.13.2 - 2016-01-06

Patch release, resolves one issue:

dart2js: Stack traces are not captured correctly (SDK issue [25235] (#25235))

1.13.1 - 2015-12-17

Patch release, resolves three issues:

VM type propagation fix: Resolves a potential crash in the Dart VM (SDK commit [dff13be] (https://github.com/dart-lang/sdk/commit/dff13bef8de104d33b04820136da2d80f3c835d7))
dart2js crash fix: Resolves a crash in pkg/js and dart2js (SDK issue [24974] (#24974))
Pub get crash on ARM: Fixes a crash triggered when running 'pub get' on ARM processors such as those on a Raspberry Pi (SDK issue [24855] (#24855))

1.13.0 - 2015-11-18

Core library changes

dart:async
- StreamController added getters for onListen, onPause, and onResume with the corresponding new typedef void ControllerCallback().
- StreamController added a getter for onCancel with the corresponding new typedef ControllerCancelCallback();
- StreamTransformer instances created with fromHandlers with no handleError callback now forward stack traces along with errors to the resulting streams.
dart:convert
- Added support for Base-64 encoding and decoding.
  - Added new classes Base64Codec, Base64Encoder, and Base64Decoder.
  - Added new top-level const Base64Codec BASE64.
dart:core
- Uri added removeFragment method.
- String.allMatches (implementing Pattern.allMatches) is now lazy, as all allMatches implementations are intended to be.
- Resource is deprecated, and will be removed in a future release.
dart:developer
- Added Timeline class for interacting with Observatory's timeline feature.
- Added ServiceExtensionHandler, ServiceExtensionResponse, and registerExtension which enable developers to provide their own VM service protocol extensions.
dart:html, dart:indexed_db, dart:svg, dart:web_audio, dart:web_gl, dart:web_sql
- The return type of some APIs changed from double to num. Dartium is now using JS interop for most operations. JS does not distinguish between numeric types, and will return a number as an int if it fits in an int. This will mostly cause an error if you assign to something typed double in checked mode. You may need to insert a toDouble() call or accept num. Examples of APIs that are affected include Element.getBoundingClientRect and TextMetrics.width.
dart:io
- Breaking: Secure networking has changed, replacing the NSS library with the BoringSSL library. SecureSocket, SecureServerSocket, RawSecureSocket,RawSecureServerSocket, HttpClient, and HttpServer now all use a SecurityContext object which contains the certificates and keys used for secure TLS (SSL) networking.
  
  This is a breaking change for server applications and for some client applications. Certificates and keys are loaded into the SecurityContext from PEM files, instead of from an NSS certificate database. Information about how to change applications that use secure networking is at https://www.dartlang.org/server/tls-ssl.html
- HttpClient no longer sends URI fragments in the request. This is not allowed by the HTTP protocol. The HttpServer still gracefully receives fragments, but discards them before delivering the request.
- To allow connections to be accepted on the same port across different isolates, set the shared argument to true when creating server socket and HttpServer instances.
  - The deprecated ServerSocketReference and RawServerSocketReference classes have been removed.
  - The corresponding reference properties on ServerSocket and RawServerSocket have been removed.
dart:isolate
- spawnUri added an environment named argument.

Tool changes

dart2js and Dartium now support improved JavaScript Interoperability via the js package.
docgen and dartdocgen no longer ship in the SDK. The docgen sources have been removed from the repository.
This is the last release to ship the VM's "legacy debug protocol". We intend to remove the legacy debug protocol in Dart VM 1.14.
The VM's Service Protocol has been updated to version 3.0 to take care of a number of issues uncovered by the first few non-observatory clients. This is a potentially breaking change for clients.
Dartium has been substantially changed. Rather than using C++ calls into Chromium internals for DOM operations it now uses JS interop. The DOM objects in dart:html and related libraries now wrap a JavaScript object and delegate operations to it. This should be mostly transparent to users. However, performance and memory characteristics may be different from previous versions. There may be some changes in which DOM objects are wrapped as Dart objects. For example, if you get a reference to a Window object, even through JS interop, you will always see it as a Dart Window, even when used cross-frame. We expect the change to using JS interop will make it much simpler to update to new Chrome versions.

1.12.2 - 2015-10-21

Core library changes

dart:io
- A memory leak in creation of Process objects is fixed.

1.12.1 - 2015-09-08

Tool changes

Pub
- Pub will now respect .gitignore when validating a package before it's published. For example, if a LICENSE file exists but is ignored, that is now an error.
- If the package is in a subdirectory of a Git repository and the entire subdirectory is ignored with .gitignore, pub will act as though nothing was ignored instead of uploading an empty package.
- The heuristics for determining when pub get needs to be run before various commands have been improved. There should no longer be false positives when non-dependency sections of the pubspec have been modified.

1.12.0 - 2015-08-31

Language changes

Null-aware operators
- ??: if null operator. expr1 ?? expr2 evaluates to expr1 if not null, otherwise expr2.
- ??=: null-aware assignment. v ??= expr causes v to be assigned expr only if v is null.
- x?.p: null-aware access. x?.p evaluates to x.p if x is not null, otherwise evaluates to null.
- x?.m(): null-aware method invocation. x?.m() invokes m only if x is not null.

Core library changes

dart:async
- StreamController added setters for the onListen, onPause, onResume and onCancel callbacks.
dart:convert
- LineSplitter added a split static method returning an Iterable.
dart:core
- Uri class now perform path normalization when a URI is created. This removes most .. and . sequences from the URI path. Purely relative paths (no scheme or authority) are allowed to retain some leading "dot" segments. Also added hasAbsolutePath, hasEmptyPath, and hasScheme properties.
dart:developer
- New log function to transmit logging events to Observatory.
dart:html
- NodeTreeSanitizer added the const trusted field. It can be used instead of defining a NullTreeSanitizer class when calling setInnerHtml or other methods that create DOM from text. It is also more efficient, skipping the creation of a DocumentFragment.
dart:io
- Added two new file modes, WRITE_ONLY and WRITE_ONLY_APPEND for opening a file write only. eaeecf2
- Change stdout/stderr to binary mode on Windows. 4205b29
dart:isolate
- Added onError, onExit and errorsAreFatal parameters to Isolate.spawnUri.
dart:mirrors
- InstanceMirror.delegate moved up to ObjectMirror.
- Fix InstanceMirror.getField optimization when the selector is an operator.
- Fix reflective NoSuchMethodErrors to match their non-reflective counterparts when due to argument mismatches. (VM only)

Tool changes

Documentation tools
- dartdoc is now the default tool to generate static HTML for API docs. Learn more.
- docgen and dartdocgen have been deprecated. Currently plan is to remove them in 1.13.
Formatter (dartfmt)
- Over 50 bugs fixed.
- Optimized line splitter is much faster and produces better output on complex code.
Observatory
- Allocation profiling.
- New feature to display output from logging.
- Heap snapshot analysis works for 64-bit VMs.
- Improved ability to inspect typed data, regex and compiled code.
- Ability to break on all or uncaught exceptions from Observatory's debugger.
- Ability to set closure-specific breakpoints.
- 'anext' - step past await/yield.
- Preserve when a variable has been expanded/unexpanded in the debugger.
- Keep focus on debugger input box whenever possible.
- Echo stdout/stderr in the Observatory debugger. Standalone-only so far.
- Minor fixes to service protocol documentation.
Pub
- Breaking: various commands that previously ran pub get implicitly no longer do so. Instead, they merely check to make sure the ".packages" file is newer than the pubspec and the lock file, and fail if it's not.
- Added support for --verbosity=error and --verbosity=warning.
- pub serve now collapses multiple GET requests into a single line of output. For full output, use --verbose.
- pub deps has improved formatting for circular dependencies on the entrypoint package.
- pub run and pub global run
  - Breaking: to match the behavior of the Dart VM, executables no longer run in checked mode by default. A --checked flag has been added to run them in checked mode manually.
  - Faster start time for executables that don't import transformed code.
  - Binstubs for globally-activated executables are now written in the system encoding, rather than always in UTF-8. To update existing executables, run pub cache repair.
- pub get and pub upgrade
  - Pub will now generate a ".packages" file in addition to the "packages" directory when running pub get or similar operations, per the package spec proposal. Pub now has a --no-package-symlinks flag that will stop "packages" directories from being generated at all.
  - An issue where HTTP requests were sometimes made even though --offline was passed has been fixed.
  - A bug with --offline that caused an unhelpful error message has been fixed.
  - Pub will no longer time out when a package takes a long time to download.
- pub publish
  - Pub will emit a non-zero exit code when it finds a violation while publishing.
  - .gitignore files will be respected even if the package isn't at the top level of the Git repository.
- Barback integration
  - A crashing bug involving transformers that only apply to non-public code has been fixed.
  - A deadlock caused by declaring transformer followed by a lazy transformer (such as the built-in $dart2js transformer) has been fixed.
  - A stack overflow caused by a transformer being run multiple times on the package that defines it has been fixed.
  - A transformer that tries to read a nonexistent asset in another package will now be re-run if that asset is later created.

VM Service Protocol Changes

BREAKING The service protocol now sends JSON-RPC 2.0-compatible server-to-client events. To reflect this, the service protocol version is now 2.0.
The service protocol now includes a "jsonrpc" property in its responses, as opposed to "json-rpc".
The service protocol now properly handles requests with non-string ids. Numeric ids are no longer converted to strings, and null ids now don't produce a response.
Some RPCs that didn't include a "jsonrpc" property in their responses now include one.

1.11.2 - 2015-08-03

Core library changes

Fix a bug where WebSocket.close() would crash if called after WebSocket.cancel().

1.11.1 - 2015-07-02

Tool changes

Pub will always load Dart SDK assets from the SDK whose pub executable was run, even if a DART_SDK environment variable is set.

1.11.0 - 2015-06-25

Core library changes

dart:core
- Iterable added an empty constructor. dcf0286
- Iterable can now be extended directly. An alternative to extending IterableBase from dart:collection.
- List added an unmodifiable constructor. r45334
- Map added an unmodifiable constructor. r45733
- int added a gcd method. a192ef4
- int added a modInverse method. f6f338c
- StackTrace added a fromString constructor. 68dd6f6
- Uri added a directory constructor. d8dbb4a
- List iterators may not throw ConcurrentModificationError as eagerly in release mode. In checked mode, the modification check is still as eager as possible. r45198
dart:developer - NEW
- Replaces the deprecated dart:profiler library.
- Adds new functions debugger and inspect. 6e42aec
dart:io
- FileSystemEntity added a uri property. 8cf32dc
- Platform added a static resolvedExecutable property. c05c8c6
dart:html
- Element methods, appendHtml and insertAdjacentHtml now take nodeValidator and treeSanitizer parameters, and the inputs are consistently sanitized. r45818 announcement
dart:isolate
- BREAKING The positional priority parameter of Isolate.ping and Isolate.kill is now a named parameter named priority.
- BREAKING Removed the Isolate.AS_EVENT priority.
- Isolate methods ping and addOnExitListener now have a named parameter response. r45092
- Isolate.spawnUri added a named argument checked.
- Remove the experimental state of the API.
dart:profiler - DEPRECATED
- This library will be removed in 1.12. Use dart:developer instead.

Tool changes

This is the first release that does not include the Eclipse-based Dart Editor. See dart.dev/tools for alternatives.
This is the last release that ships the (unsupported) dart2dart (aka dart2js --output-type=dart) utility as part of dart2js

1.10.0 - 2015-04-29

Core library changes

dart:convert
- POTENTIALLY BREAKING Fix behavior of HtmlEscape. It no longer escapes no-break space (U+00A0) anywhere or forward slash (/, U+002F) in element context. Slash is still escaped using HtmlEscapeMode.UNKNOWN. r45003, r45153, r45189
dart:core
- Uri.parse added start and end positional arguments.
dart:html
- POTENTIALLY BREAKING CssClassSet method arguments must now be 'tokens', i.e. non-empty strings with no white-space characters. The implementation was incorrect for class names containing spaces. The fix is to forbid spaces and provide a faster implementation. Announcement
dart:io
- ProcessResult now exposes a constructor.
- import and Isolate.spawnUri now supports the Data URI scheme on the VM.

Tool Changes

pub

Running pub run foo within a package now runs the foo executable defined by the foo package. The previous behavior ran bin/foo. This makes it easy to run binaries in dependencies, for instance pub run test.
On Mac and Linux, signals sent to pub run and forwarded to the child command.

1.9.3 - 2015-04-14

This is a bug fix release which merges a number of commits from bleeding_edge.

dart2js: Addresses as issue with minified JavaScript output with CSP enabled - r44453
Editor: Fixes accidental updating of files in the pub cache during rename refactoring - r44677
Editor: Fix for issue 23032 regarding skipped breakpoints on Windows - r44824
dart:mirrors: Fix MethodMirror.source when the method is on the first line in a script - r44957, r44976
pub: Fix for issue 23084: Pub can fail to load transformers necessary for local development - r44876

1.9.1 - 2015-03-25

Language changes

Support for async, await, sync*, async*, yield, yield*, and await for. See the the language tour for more details.
Enum support is fully enabled. See the language tour for more details.

Tool changes

The formatter is much more comprehensive and generates much more readable code. See its tool page for more details.
The analysis server is integrated into the IntelliJ plugin and the Dart editor. This allows analysis to run out-of-process, so that interaction remains smooth even for large projects.
Analysis supports more and better hints, including unused variables and unused private members.

Core library changes

Highlights

There's a new model for shared server sockets with no need for a Socket reference.
A new, much faster regular expression engine.
The Isolate API now works across the VM and dart2js.

Details

For more information on any of these changes, see the corresponding documentation on the Dart API site.

dart:async:
- Future.wait added a new named argument, cleanUp, which is a callback that releases resources allocated by a successful Future.
- The SynchronousStreamController class was added as an explicit name for the type returned when the sync argument is passed to new StreamController.
dart:collection: The new SplayTreeSet.from(Iterable) constructor was added.
dart:convert: Utf8Encoder.convert and Utf8Decoder.convert added optional start and end arguments.
dart:core:
- RangeError added new static helper functions: checkNotNegative, checkValidIndex, checkValidRange, and checkValueInInterval.
- int added the modPow function.
- String added the replaceFirstMapped and replaceRange functions.
dart:io:
- Support for locking files to prevent concurrent modification was added. This includes the File.lock, File.lockSync, File.unlock, and File.unlockSync functions as well as the FileLock class.
- Support for starting detached processes by passing the named mode argument (a ProcessStartMode) to Process.start. A process can be fully attached, fully detached, or detached except for its standard IO streams.
- HttpServer.bind and HttpServer.bindSecure added the v6Only named argument. If this is true, only IPv6 connections will be accepted.
- HttpServer.bind, HttpServer.bindSecure, ServerSocket.bind, RawServerSocket.bind, SecureServerSocket.bind and RawSecureServerSocket.bind added the shared named argument. If this is true, multiple servers or sockets in the same Dart process may bind to the same address, and incoming requests will automatically be distributed between them.
- Deprecation: the experimental ServerSocketReference and RawServerSocketReference classes, as well as getters that returned them, are marked as deprecated. The shared named argument should be used instead. These will be removed in Dart 1.10.
- Socket.connect and RawSocket.connect added the sourceAddress named argument, which specifies the local address to bind when making a connection.
- The static Process.killPid method was added to kill a process with a given PID.
- Stdout added the nonBlocking instance property, which returns a non-blocking IOSink that writes to standard output.
dart:isolate:
- The static getter Isolate.current was added.
- The Isolate methods addOnExitListener, removeOnExitListener, setErrorsFatal, addOnErrorListener, and removeOnErrorListener now work on the VM.
- Isolates spawned via Isolate.spawn now allow most objects, including top-level and static functions, to be sent between them.

1.8.5 - 2015-01-21

Code generation for SIMD on ARM and ARM64 is fixed.
A possible crash on MIPS with newer GCC toolchains has been prevented.
A segfault when using rethrow was fixed (issue 21795).

1.8.3 - 2014-12-10

Breakpoints can be set in the Editor using file suffixes (issue 21280).
IPv6 addresses are properly handled by HttpClient in dart:io, fixing a crash in pub (issue 21698).
Issues with the experimental async/await syntax have been fixed.
Issues with a set of number operations in the VM have been fixed.
ListBase in dart:collection always returns an Iterable with the correct type argument.

1.8.0 - 2014-11-28

dart:collection: SplayTree added the toSet function.
dart:convert: The JsonUtf8Encoder class was added.
dart:core:
- The IndexError class was added for errors caused by an index being outside its expected range.
- The new RangeError.index constructor was added. It forwards to new IndexError.
- RangeError added three new properties. invalidProperty is the value that caused the error, and start and end are the minimum and maximum values that the value is allowed to assume.
- new RangeError.value and new RangeError.range added an optional message argument.
- The new String.fromCharCodes constructor added optional start and end arguments.
dart:io:
- Support was added for the Application-Layer Protocol Negotiation extension to the TLS protocol for both the client and server.
- SecureSocket.connect, SecureServerSocket.bind, RawSecureSocket.connect, RawSecureSocket.secure, RawSecureSocket.secureServer, and RawSecureServerSocket.bind added a supportedProtocols named argument for protocol negotiation.
- RawSecureServerSocket added a supportedProtocols field.
- RawSecureSocket and SecureSocket added a selectedProtocol field which contains the protocol selected during protocol negotiation.

1.7.0 - 2014-10-15

Tool changes

pub now generates binstubs for packages that are globally activated so that they can be put on the user's PATH and used as normal executables. See the pub global activate documentation.
When using dart2js, deferred loading now works with multiple Dart apps on the same page.

Core library changes

dart:async: Zone, ZoneDelegate, and ZoneSpecification added the errorCallback function, which allows errors that have been programmatically added to a Future or Stream to be intercepted.
dart:io:
- Breaking change: HttpClient.close must be called for all clients or they will keep the Dart process alive until they time out. This fixes the handling of persistent connections. Previously, the client would shut down immediately after a request.
- Breaking change: HttpServer no longer compresses all traffic by default. The new autoCompress property can be set to true to re-enable compression.
dart:isolate: Isolate.spawnUri added the optional packageRoot argument, which controls how it resolves package: URIs.

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