TestDataAnalyzer: detect Func<T> by symbol instead of display-string prefix

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
75/100
Issue type
Refactor
Clarity
Clearly specified
Activity status
Active
Tech stack
csharp
Domain
testing

Research direction

The three display-string checks are at src/TUnit.Analyzers/TestDataAnalyzer.cs lines 548, 569 and 870; line 870 may live on the branch from #7347 rather than main. Look at how TestDataRow1 is already compared by symbol in the same file and mirror that pattern. Done means all three sites compare OriginalDefinition against a System.Func1 symbol resolved once per compilation, and tests/TUnit.Analyzers.Tests still pass.

Written by the indexing model from the issue text.

Description

enhancement P3 performance

TestDataAnalyzer detects Func<T> by calling ToDisplayString().StartsWith("System.Func<", StringComparison.Ordinal). This allocates a display string during analysis and relies on formatting instead of symbol identity.

Current code

Following merged PR #7347 (#7227), the three checks are:

  • Two property-injection checks in src/TUnit.Analyzers/TestDataAnalyzer.cs, using funcType and funcTypeForError.
  • TryUnwrapFunc in the same file, called while peeling the supported data-row wrappers.

Both automated reviewers raised this as non-blocking on #7347 (review comment). That prerequisite has merged; this issue is available for implementation.

Acceptance criteria

  • Resolve System.Func`1 once per compilation with Compilation.GetTypeByMetadataName("System.Func`1").
  • Compare OriginalDefinition with SymbolEqualityComparer.Default in all three checks, as the analyzer already does for TestDataRow<T>.
  • Preserve the existing wrapper-peeling order and property-injection behavior.
  • Add analyzer cases for Func<TestDataRow<(int, int)>> and TestDataRow<Func<(int, int)>> against an (int a, int b) test signature. These are regression coverage for the existing tuple expansion after wrapper peeling; there is no known defect in that ordering.
  • Run the relevant TUnit.Analyzers.Tests coverage.
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Merged PRs (30d)
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