GROOVY-12292: Honour method-level type-checking annotations over class-level SKIP

[paulk-asert]

GROOVY-12292: https://issues.apache.org/jira/browse/GROOVY-12292

A method-level @TypeChecked or @CompileStatic annotation with the default
(non-SKIP) mode was silently ignored when the declaring class carried a
SKIP-mode annotation. Four combinations were affected:

• @CompileDynamic class + @CompileStatic method
• @CompileStatic(SKIP) class + @CompileStatic method
• @TypeChecked(SKIP) class + @CompileStatic method
• @TypeChecked(SKIP) class + @TypeChecked method

The cause is in StaticTypeCheckingVisitor#isSkipMode, which recursed to the
declaring class without first considering that the method's own annotation had
already answered the question. Nested classes take a different code path and
already honour the more specific annotation (GROOVY-10238), as does the
opt-out direction (checked class + SKIP method), making methods the lone
anomaly. The behaviour is longstanding (reproduced identically on 4.0.27,
5.0.6 and 6.0.0-alpha-1).

The fix stops the walk up to the declaring class when the node itself carries
one of the visitor's type-checking annotations with a non-SKIP mode: the most
specific annotation wins, and a class-level SKIP remains the default for
members without their own annotation. Because StaticCompileTransformation
derives the STATIC_COMPILE_NODE metadata from the same method, bytecode
generation follows: an opted-in method under a @CompileDynamic class is now
statically compiled, not just checked (asserted in the new bytecode test).

Deliberately unchanged, now ratified by tests and documentation:

• opt-out direction: SKIP-mode methods inside checked classes are skipped as
  before;
• cross-family behaviour: method-level @CompileStatic(SKIP) /
  @CompileDynamic disables static compilation but does not exempt the
  method from an enclosing class's @TypeChecked checking; only
  @TypeChecked(SKIP) does.

Since the change means previously-dynamic (and unchecked) method bodies are
now checked and statically compiled, it is behaviour-changing: a
COMPATIBILITY.md entry is included and the JIRA issue should get the
breaking label, targeting 6.0 only. Documentation of the precedence rules
is added to the "Skipping sections" part of core-semantics.adoc.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.6076%. Comparing base (3190f42) to head (47dffb3).

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2829        +/-   ##
==================================================
- Coverage     70.6100%   70.6076%   -0.0023%     
  Complexity      36472      36472                
==================================================
  Files            1569       1569                
  Lines          133831     133834         +3     
  Branches        24666      24667         +1     
==================================================
- Hits            94498      94497         -1     
- Misses          30821      30823         +2     
- Partials         8512       8514         +2     

Files with missing lines	Coverage Δ
...roovy/transform/stc/StaticTypeCheckingVisitor.java	87.2602% <100.0000%> (+0.0094%)	⬆️

... and 7 files with indirect coverage changes

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: 47dffb3
▶️ Tests: 113057 executed
⚪️ Checks: 31/31 completed

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[Copilot]

Pull request overview

Fixes GROOVY-12292 by ensuring method/constructor-level @TypeChecked / @CompileStatic opt-ins (non-SKIP) take precedence over an enclosing class’s SKIP/@CompileDynamic, aligning method behavior with nested-class precedence rules and ensuring static compilation metadata is set consistently.

Changes:

• Update StaticTypeCheckingVisitor#isSkipMode to stop inheriting SKIP from the declaring class when the node itself has an explicit non-SKIP type-checking annotation.
• Add regression tests covering the previously-broken annotation combinations, including a bytecode-level assertion that an opted-in method under @CompileDynamic is truly statically compiled.
• Document the precedence rules in the language spec and record the behavior change in COMPATIBILITY.md (targeting Groovy 6).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/main/java/org/codehaus/groovy/transform/stc/StaticTypeCheckingVisitor.java	Adjusts isSkipMode resolution so explicit non-SKIP annotations on a node override enclosing SKIP.
src/test/groovy/org/codehaus/groovy/classgen/asm/sc/CompileDynamicTest.groovy	Adds regression + bytecode tests for @CompileStatic methods inside @CompileDynamic / SKIP classes.
src/test/groovy/groovy/transform/stc/TypeCheckingModeTest.groovy	Adds regression tests for @TypeChecked opt-in inside @TypeChecked(SKIP) and cross-family @CompileStatic(SKIP) behavior under @TypeChecked.
src/spec/doc/core-semantics.adoc	Documents “most specific annotation wins” precedence and clarifies cross-family opt-out behavior.
COMPATIBILITY.md	Adds Groovy 6 compatibility note describing the behavior change and impact.

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