Reduce allocations around empty ReadOnlyCollections #76097
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- Add an internal (for now) `ReadOnlyCollection<T>.Empty` - Return the singleton `ReadOnlyCollection<T>.Empty` from `Array.AsReadOnly` when the source is empty - Return a singleton empty enumerator from an empty `ReadOnlyCollection<T>` - Fix up some reflection code to avoid unnecessary `ReadOnlyCollection<T>` allocations (e.g. just to wrap empty arrays) - Fix a null reference bug in RuntimeCustomAttributeData.NamedArguments (I don't know if it's actually reachable, but this property shouldn't be returning null) - Avoid a few unnecessary allocations in TimeZoneInfo.GetSystemTimeZones
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I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label. |
ghost
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Tagging subscribers to this area: @dotnet/area-system-collections Issue Details
Contributes to #76028
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jkotas
reviewed
Sep 23, 2022
src/libraries/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyCollection.cs
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jkotas
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Sep 23, 2022
src/libraries/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyCollection.cs
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That would be a breaking change for code like var list = new List<int>();
ReadOnlyCollection<int> readOnly = list.AsReadOnly();
list.Add(42);
Debug.Assert(readOnly.Count == 1);However, the PR does not actually include such a change, as it does not modify src/libraries/System.Private.CoreLib/src/System/Collections/Generic/List.cs. |
Yes, that's why it doesn't. I wrote the description before I actually implemented things, thought I removed that part of the description, but apparently didn't. |
src/libraries/Common/tests/System/Collections/IEnumerable.Generic.Tests.cs
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eiriktsarpalis
approved these changes
Sep 26, 2022
krwq
reviewed
Sep 27, 2022
src/libraries/Common/tests/System/Collections/IDictionary.Generic.Tests.cs
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krwq
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Sep 27, 2022
...ries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs
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ReadOnlyCollection<T>.EmptyReadOnlyCollection<T>.EmptyfromArray.AsReadOnlywhen the source is emptyReadOnlyCollection<T>ReadOnlyCollection<T>allocations (e.g. just to wrap empty arrays)Contributes to #76028