GROOVY-11878: Invariant loops spike

[paulk-asert]

There are two commits:

• The first commit contains the proposed grammar and AST plumbing changes. It includes changes to plumb the existing @Invariant annotation into loops within the groovy-contracts subproject. There isn't support for other annotations like @Ensures (see example GROOVY-11878) yet which languages like Dafny support. This could be considered for a subsequent PR.

• The second commit contains a second @Parallel example AST transform (see example in GROOVY-11878). It isn't meant to be production quality or included in the merge of this PR, but is another useful check that the AST plumbing changes are working. In particular, the @Parallel transform doesn't attempt to do any state sharing (bar the loop variable) or protection, it's just a demo.

Future work:

• At present no validation of target type is handled. For now, AST transforms using this feature should do whatever checks they deem appropriate on target type within the transform. We have additional work to do to be able to automatically do the checking. E.g. We could add enums/annotations so that we could do something like: @ExtendedTarget(ExtendedTargetType.LOOP) to an @interface definition. Then we could give appropriate error messages when the annotations were used incorrectly.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.36496% with 68 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.6566%. Comparing base (b9c4135) to head (cdf0c51).

Files with missing lines	Patch %	Lines
...us/groovy/transform/ParallelASTTransformation.java	0.0000%	34 Missing ⚠️
...pache/groovy/contracts/LoopInvariantViolation.java	12.5000%	14 Missing ⚠️
.../contracts/ast/LoopInvariantASTTransformation.java	58.3333%	5 Missing and 5 partials ⚠️
.../apache/groovy/contracts/domain/LoopInvariant.java	0.0000%	5 Missing ⚠️
...pache/groovy/parser/antlr4/SemanticPredicates.java	82.3529%	0 Missing and 3 partials ⚠️
...n/java/org/codehaus/groovy/ast/AnnotationNode.java	0.0000%	1 Missing ⚠️
...aus/groovy/transform/ASTTransformationVisitor.java	83.3333%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2400        +/-   ##
==================================================
- Coverage     66.6744%   66.6566%   -0.0178%     
- Complexity      29856      29887        +31     
==================================================
  Files            1382       1386         +4     
  Lines          116145     116278       +133     
  Branches        20481      20504        +23     
==================================================
+ Hits            77439      77507        +68     
- Misses          32361      32421        +60     
- Partials         6345       6350         +5     

Files with missing lines	Coverage Δ
...haus/groovy/transform/ASTTestTransformation.groovy	85.5072% <100.0000%> (ø)
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	86.5436% <100.0000%> (+0.0364%)	⬆️
...aus/groovy/ast/ClassCodeExpressionTransformer.java	100.0000% <100.0000%> (ø)
...g/codehaus/groovy/ast/ClassCodeVisitorSupport.java	100.0000% <100.0000%> (ø)
...n/java/org/codehaus/groovy/ast/stmt/Statement.java	100.0000% <100.0000%> (ø)
...va/org/codehaus/groovy/control/ResolveVisitor.java	89.6334% <100.0000%> (+0.0527%)	⬆️
...ansform/ASTTransformationCollectorCodeVisitor.java	91.1392% <100.0000%> (+0.2301%)	⬆️
...n/java/org/codehaus/groovy/ast/AnnotationNode.java	69.2308% <0.0000%> (-0.6721%)	⬇️
...aus/groovy/transform/ASTTransformationVisitor.java	81.8681% <83.3333%> (+0.0499%)	⬆️
...pache/groovy/parser/antlr4/SemanticPredicates.java	83.5294% <82.3529%> (-0.2941%)	⬇️
... and 4 more

... and 4 files with indirect coverage changes

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