GROOVY-12013: New optional type checking extension: CombinerChecker t…

[paulk-asert]

…o verify associative combiners in injectParallel/sumParallel/Stream.reduce

https://issues.apache.org/jira/browse/GROOVY-12013

[Copilot]

Pull request overview

Adds a new incubating type-checking extension to help catch incorrect combiners used with parallel reductions (Groovy’s sumParallel/injectParallel and JDK Stream#reduce), plus supporting annotations and documentation so users can declare/verify associativity and identity-element contracts.

Changes:

• Introduces groovy.typecheckers.CombinerChecker with lenient/strict modes and Monoid/Semigroup carrier recognition.
• Adds new @Associative and @Reducer annotations in groovy.transform to declare combiner contracts (including optional identity via zero).
• Adds spike-style tests and expands the typecheckers guide with a new section describing the checker and usage.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
subprojects/groovy-typecheckers/src/main/groovy/groovy/typecheckers/CombinerChecker.groovy	New type-checking extension that analyzes combiners for parallel reductions and stream reductions.
subprojects/groovy-typecheckers/src/test/groovy/groovy/typecheckers/CombinerCheckerTest.groovy	New tests covering lenient/strict behavior, carrier recognition, and stream reduce handling.
subprojects/groovy-typecheckers/src/spec/doc/typecheckers.adoc	Documentation entry + full section describing CombinerChecker behavior and configuration.
src/main/java/groovy/transform/Associative.java	New annotation to declare associativity contract for combiners.
src/main/java/groovy/transform/Reducer.java	New annotation to declare associativity + identity contract (optional zero).

[codecov-commenter]

Codecov Report

❌ Patch coverage is 68.33333% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.1668%. Comparing base (293ebc5) to head (fcc8913).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
.../groovy/groovy/typecheckers/CombinerChecker.groovy	68.3333%	4 Missing and 34 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2536        +/-   ##
==================================================
+ Coverage     68.1641%   68.1668%   +0.0028%     
- Complexity      32862      32901        +39     
==================================================
  Files            1499       1500         +1     
  Lines          125396     125520       +124     
  Branches        22666      22717        +51     
==================================================
+ Hits            85475      85563        +88     
- Misses          32408      32412         +4     
- Partials         7513       7545        +32     

Files with missing lines	Coverage Δ
.../groovy/groovy/typecheckers/CombinerChecker.groovy	68.3333% <68.3333%> (ø)

... and 6 files with indirect coverage changes

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[testlens-app]

✅ All tests passed ✅

🏷️ Commit: fcc8913
▶️ Tests: 99254 executed
⚪️ Checks: 28/28 completed

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