GROOVY-12289: Switch expressions with duplicate case labels compile under @TypeChecked but fail under @CompileStatic

[paulk-asert]

See: https://issues.apache.org/jira/browse/GROOVY-12289

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.2651%. Comparing base (01f91d4) to head (7dedae9).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...sgen/asm/sc/StaticTypesSwitchExpressionWriter.java	75.0000%	0 Missing and 1 partial ⚠️
...roovy/transform/stc/StaticTypeCheckingVisitor.java	91.6667%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2826        +/-   ##
==================================================
+ Coverage     70.2594%   70.2651%   +0.0057%     
- Complexity      36274      36283         +9     
==================================================
  Files            1569       1569                
  Lines          133723     133725         +2     
  Branches        24637      24638         +1     
==================================================
+ Hits            93953      93962         +9     
+ Misses          31257      31249         -8     
- Partials         8513       8514         +1     

Files with missing lines	Coverage Δ
...sgen/asm/sc/StaticTypesSwitchExpressionWriter.java	93.9394% <75.0000%> (+0.1894%)	⬆️
...roovy/transform/stc/StaticTypeCheckingVisitor.java	87.1972% <91.6667%> (+0.0133%)	⬆️

... and 10 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR addresses GROOVY-12289 by making duplicate constant case labels in switch expressions consistently rejected by the static type checker (so @TypeChecked and @CompileStatic fail the same way), while preserving dynamic “first match wins” behavior when type checking is explicitly bypassed (e.g., TypeCheckingMode.SKIP or a type-checking extension).

Changes:

• Add a static type checking pass that detects duplicate constant case labels (int-family, String, enum constants) in switch expressions and reports a consistent STC error.
• Update the static switch-expression bytecode writer to treat duplicates (when type checking is bypassed) as a reason to skip intrinsic switch optimizations and fall back to sequential dispatch.
• Add regression tests covering dynamic semantics, STC/SC error reporting, skip-mode fallback behavior, and an extension-based “escape hatch”.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/test/groovy/org/codehaus/groovy/classgen/Jep361SwitchExpressionTest.groovy	Adds coverage for duplicate-label behavior across dynamic, @TypeChecked, and @CompileStatic.
src/test/groovy/org/codehaus/groovy/classgen/asm/sc/SwitchExpressionStaticCompileTest.groovy	Updates expected error messaging and adds a skip-mode fallback test for sequential dispatch semantics.
src/test/groovy/groovy/transform/stc/TypeCheckingExtensionsTest.groovy	Adds a test demonstrating a type-checking extension can opt a DSL method out of the duplicate-label error.
src/test-resources/groovy/transform/stc/Groovy12289Extension.groovy	Introduces the STC extension used by the new escape-hatch test.
src/main/java/org/codehaus/groovy/transform/stc/StaticTypeCheckingVisitor.java	Implements duplicate constant label detection during STC for switch expressions.
src/main/java/org/codehaus/groovy/classgen/asm/sc/StaticTypesSwitchExpressionWriter.java	Removes late duplicate-label hard error and instead skips optimizer to allow sequential dispatch when checking is bypassed.

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: ec38a5d
▶️ Tests: 111722 executed
⚪️ Checks: 31/31 completed

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