ILLink.RoslynAnalyzer: fix hole for new constraint

[sbomer]

The new constraint processing was happening in a separate code path from the other generic argument processing, and that code path didn't see the implicit call to the base ctor (because it didn't use the IOperation tree). This fixes it by moving the new constraint processing into GenericArgumentDataFlow.

Unlike ILC, the analyzer can't just treat new() the same as PublicParameterlessConstructors, because it needs to produce analysis warnings for RequiresDynamicCode or RequiresAssemblyFiles accessed via new() constraint, even when trim analysis is disabled (the annotation is treated as reflection access, but new() is not).

Fixes #118869

[Copilot]

Pull Request Overview

This PR fixes a hole in the ILLink.RoslynAnalyzer's handling of generic constraints. The analyzer was not properly detecting required capability violations (like RequiresDynamicCode or RequiresAssemblyFiles) when accessed through new() constraints on generic type parameters. The fix moves the new constraint processing from a separate code path into the existing GenericArgumentDataFlow class, ensuring that implicit constructor calls are properly analyzed.

Key changes:

• Consolidates generic constraint processing into GenericArgumentDataFlow
• Adds proper detection of new() constraint violations for required capabilities
• Updates test cases to verify the fix works correctly

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
RequiresOnClass.cs	Adds test cases for new constraint processing and updates expected warnings
TrimAnalysisVisitor.cs	Updates method signatures to pass DataFlowAnalyzerContext
TrimAnalysisMethodCallPattern.cs	Updates HandleCall invocation with new parameters
TrimAnalysisGenericInstantiationPattern.cs	Refactors to use GenericArgumentDataFlow instance instead of static methods
TrimAnalysisAssignmentPattern.cs	Updates RequireDynamicallyAccessedMembersAction constructor call
RequireDynamicallyAccessedMembersAction.cs	Adds DataFlowAnalyzerContext and FeatureContext parameters
HandleCallAction.cs	Updates constructor to accept and pass through new context parameters
GenericArgumentDataFlow.cs	Major refactor from static to instance class with new constraint processing
RequiresAnalyzerBase.cs	Removes old generic name syntax processing logic
DynamicallyAccessedMembersAnalyzer.cs	Updates to use new GenericArgumentDataFlow instance

[jtschuster]

Sorry I got to this so late!

[sbomer]

No problem, thanks for the review!