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fix: annotated argument's `var` node type is explicit, not inferred by bzoracler · Pull Request #17217 · python/mypy · GitHub
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fix: annotated argument's var node type is explicit, not inferred #17217

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Merged
merged 1 commit into from
May 21, 2024
Merged

fix: annotated argument's var node type is explicit, not inferred #17217

merged 1 commit into from
May 21, 2024

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bzoracler
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Fixes #17216

During conversion from a standard library AST to the mypy AST, Var nodes were being created inside Argument nodes without acknowledging the presence of a type annotation, leading to the Var node's type as being always set as inferred:

mypy/mypy/nodes.py

Line 988 in fb31409

self.is_inferred = self.type is None

This causes an error at

mypy/mypyc/irbuild/expression.py

Lines 161 to 164 in fb31409

and expr.node.is_inferred
):
builder.error(
'Local variable "{}" has inferred type None; add an annotation'.format(

The fix simply acknowledges any presence of a type annotation, so the type of the relevant Var node is no longer considered inferred if an annotation is present.

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github-actions bot commented May 6, 2024

Diff from mypy_primer, showing the effect of this PR on open source code:

spark (https://github.com/apache/spark)
+ python/pyspark/core/rdd.py:1662: error: Function does not return a value (it only ever returns None)  [func-returns-value]
+ python/pyspark/core/rdd.py:1664: error: Unused "type: ignore" comment  [unused-ignore]

@bzoracler
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bzoracler commented May 6, 2024 •
edited
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Primer outputs look OK:

  • First warning is correct
  • Second warning (overloads) stems from an unrelated bug: 
    from collections.abc import Callable

f: Callable[[object], None] = lambda _: None

a = f("a")  # Correct error: Function does not return a value (it only ever returns None) [func-returns-value]
reveal_type(a)  # Bug: revealed type is `Any` (should be `None`)

hauntsaninja
hauntsaninja approved these changes May 21, 2024
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Thanks!

@hauntsaninja hauntsaninja merged commit ca393dd into python:master May 21, 2024
@bzoracler bzoracler deleted the fix/var-type-inferred branch May 22, 2024 20:21
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@hauntsaninja hauntsaninja hauntsaninja approved these changes

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[mypyc] ... inferred type None; add an annotation on fully-annotated code

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@bzoracler @hauntsaninja