Add basic instrumentation tests for union declarations

[AlekseyTs]

Microsoft Reviewers: Open in CodeFlow

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[Copilot]

Pull request overview

Adds initial coverage ensuring C# union-generated members interact correctly with various emit-time instrumentation modes (stack overflow probing, module cancellation, local state tracing, and dynamic analysis/test-coverage instrumentation).

Changes:

• Add UnionDeclaration_01 tests to multiple instrumentation test suites to validate which synthesized union members are/aren’t instrumented.
• Update local CompileAndVerify helpers in the Emit2 instrumentation suites to accept CSharpTestSource, enabling collection-expression sources while still applying the suite’s EmitOptions.
• Add a dynamic analysis test asserting union-generated members remain uninstrumented under test-coverage instrumentation in both Release and Debug.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Compilers/CSharp/Test/Emit2/Emit/RuntimeProbing/StackOverflowProbingTests.cs	Adds a union declaration test validating stack overflow probing instrumentation behavior.
src/Compilers/CSharp/Test/Emit2/Emit/RuntimeProbing/ModuleCancellationTests.cs	Adds a union declaration test validating module cancellation instrumentation behavior; also updates helper signature.
src/Compilers/CSharp/Test/Emit2/Emit/LocalStateTracing/LocalStateTracingTests.cs	Adds a union declaration test validating local state tracing instrumentation behavior; updates helper signatures.
src/Compilers/CSharp/Test/Emit/Emit/DynamicAnalysis/DynamicInstrumentationTests.cs	Adds a union declaration test asserting union-generated members are not test-coverage instrumented (Release + Debug).

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[AlekseyTs]

@RikkiGibson, @jjonescz Please review

[jjonescz]

Should we be using the locally defined CompileAndVerify helper which passes

emitOptions: EmitOptions.Default.WithInstrumentationKinds(ImmutableArray.Create(InstrumentationKind.TestCoverage))

instead of the base class helper?

[AlekseyTs]

Good catch! Overloading base helpers is fragile because the new overloads might not be used by a specific call site.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

src/Compilers/CSharp/Test/Emit2/Emit/LocalStateTracing/LocalStateTracingTests.cs:210

• CompileAndVerifyFails takes an expectedOutput parameter but then always passes expectedOutput: null to the underlying CompileAndVerify, so the parameter is effectively ignored (and can be misleading when trying to diagnose failures). Since there are no call sites in the repo, consider removing the parameter (and the conditional exe/dll option selection) to make the helper’s intent unambiguous.

        // Only used to diagnose test verification failures (rename CompileAndVerify to CompileAndVerifyFails and rerun).
        public CompilationVerifier CompileAndVerifyFails(CSharpTestSource source, string? ilVerifyMessage = null, string? expectedOutput = null)
            => CompileAndVerify(
                source,
                options: (expectedOutput != null) ? TestOptions.UnsafeDebugExe : TestOptions.UnsafeDebugDll,
                emitOptions: s_emitOptions,
                verify: Verification.Fails,
                targetFramework: s_targetFramework,
                expectedOutput: null);