[release/10.0] Add trim analyzer support for C# 14 extensions #119195
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Fixes dotnet#115949 This adds Roslyn analyzer support for C# 14 extensions. A few notes on the behavior: - DAM is supported on method return/params, including on property accessor return/param. - DAM is not supported on extension properties (see dotnet#119113) - DAM is not supported on extension methods (this produces IL2041) - There's still a bug with the behavior for ILLink/ILC due to the annotations not being preserved into the implementation when lowering: dotnet/roslyn#80017. Includes an update to Microsoft.CodeAnalysis for new analyzer APIs involving extension members. dotnet#119159 tracks fixing new warnings that are suppressed for now. New tests uncovered an analyzer issue with operators in the (extension or not): dotnet#119110. This change includes test coverage for non-extension operators. They also uncovered an issue that looks like a race condition in ILC: dotnet#119155.
github-actions
bot
added
the
area-Tools-ILLink
There was a problem hiding this comment.
Pull Request Overview
This PR adds support for C# 14 extension members to the IL linker's trim analyzer to fix analyzer crashes when encountering these new language features. The implementation includes handling for extension parameters on types, operator overloads, and extension properties while maintaining compatibility with existing features.
Key changes:
- Enhanced parameter handling for extension members with parameters on types
- Added test coverage for extension member data flow analysis scenarios
- Updated Microsoft.CodeAnalysis dependency to support C# 14 features
Reviewed Changes
Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| eng/Versions.props | Updates Microsoft.CodeAnalysis version to 4.14.0 for C# 14 support |
| src/tools/illink/src/ILLink.RoslynAnalyzer/IMethodSymbolExtensions.cs | Adds HasExtensionParameterOnType() method and updates parameter count calculations |
| src/tools/illink/src/ILLink.RoslynAnalyzer/TrimAnalysis/ParameterProxy.cs | Refactors constructor and property handling for extension parameters |
| src/tools/illink/src/ILLink.RoslynAnalyzer/TrimAnalysis/MethodParameterValue.cs | Removes obsolete constructors for cleaner parameter value creation |
| src/tools/illink/src/ILLink.RoslynAnalyzer/TrimAnalysis/TrimAnalysisVisitor.cs | Updates parameter reference handling for extension members |
| src/tools/illink/src/ILLink.RoslynAnalyzer/TrimAnalysis/FlowAnnotations.cs | Prevents property-level DAM propagation for extension properties |
| src/tools/illink/src/ILLink.RoslynAnalyzer/DataFlow/LocalDataFlowVisitor.cs | Handles extension property access and method calls with extension parameters |
| src/tools/illink/src/ILLink.RoslynAnalyzer/DynamicallyAccessedMembersAnalyzer.cs | Skips DAM conflict checks for extension properties |
| src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/ResultChecker.cs | Adds workaround to skip inherited attributes on compiler-generated extension types |
| src/coreclr/tools/aot/ILCompiler.Trimming.Tests/TestCasesRunner/ResultChecker.cs | Same workaround as above for NativeAOT tests |
| src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/ExtensionsDataFlow.cs | New test file for basic extension method data flow scenarios |
| src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/ExtensionMembersDataFlow.cs | New comprehensive test file for C# 14 extension member features |
| src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/MethodReturnParameterDataFlow.cs | Adds operator return value test cases |
| src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/MethodParametersDataFlow.cs | Adds operator parameter test cases |
| src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/TestChecker.cs | Adds operator declaration visitor support |
| src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/DataFlowTests.cs | Registers new test cases for execution |
| src/tools/illink/src/ILLink.RoslynAnalyzer/ILLink.RoslynAnalyzer.csproj | Removes conditional suppression of CS0436 warnings |
| Directory.Build.props | Adds IDE warning suppressions for redundant equality and unused parameters |
dotnet-policy-service
bot
added
the
linkable-framework
|
Tagging subscribers to this area: @dotnet/illink |
jeffschwMSFT
approved these changes
Aug 29, 2025
jeffschwMSFT
added
Servicing-approved
agocke
approved these changes
Aug 29, 2025
src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/MethodParametersDataFlow.cs
Outdated
Show resolved
Hide resolved
jtschuster
approved these changes
Aug 29, 2025
sbomer
added a commit
that referenced
this pull request
Sep 4, 2025
Porting feedback from #119195 to main.
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Backport of #119017 to release/10.0
Customer Impact
Reported in #115949 and #118025 as an analyzer crash when analyzing code with C# 14 extension members.
A temporary fix was put in place to avoid the crash, but it did not include support for analyzing extension members. The impact is missing or unexpected warnings when adding trim annotations for extension members.
Regression
Testing
Added testcases to cover annotations for extension members.
Risk
Low. Analyzer-only fix. Note that it does include an update to Microsoft.CodeAnalysis, which needs to remain compatible with the version that ships with VS. Confirmed with @jkoritzinsky that this version is OK for .NET 10.