Remove IList.Contains use from OfType #119600
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Pull Request Overview
This PR removes the optimization in OfType<T>().Contains() that delegated to IList.Contains() to fix correctness issues when the source contains items that compare equal but are not of the target type, and to handle multidimensional arrays properly.
- Removes the
IList.Contains()delegation optimization fromOfTypeIterator<TResult>.Contains() - Adds comprehensive test coverage for multidimensional arrays with
OfType() - Adds test coverage for the type filtering behavior when objects compare equal but are different types
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs | Removes IList.Contains optimization and adds detailed comment explaining why direct iteration is necessary |
| src/libraries/System.Linq/tests/OfTypeTests.cs | Adds tests for multidimensional arrays and type filtering behavior with custom equality |
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Tagging subscribers to this area: @dotnet/area-system-linq |
jkotas
approved these changes
Sep 11, 2025
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Author
|
/backport to release/10.0 |
Contributor
|
Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17660453305 |
4 tasks
skyoxZ
reviewed
Sep 12, 2025
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Fixes #119569