GROOVY-11998: Better support of intersection types by paulk-asert · Pull Request #2518 · apache/groovy

paulk-asert · 2026-05-06T09:06:20Z

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Copilot

Pull request overview

This PR implements parser/AST, type-checking, and codegen/runtime support for intersection-type cast and as coercion (GROOVY-11998), including marker-interface threading for lambdas/method references and a runtime fallback path for non-functional sources. It also includes a related fix for proxy generation when mixing bootstrap-loaded and user-loaded interfaces (GROOVY-11999), plus extensive tests and spec documentation updates.

Changes:

Extend the ANTLR grammar + AST builder to parse intersection types in cast targets and as coercion targets, producing an IntersectionTypeClassNode.
Add resolution + STC support for intersection targets and propagate marker-interface metadata into indy lambda/method-reference generation.
Route non-functional intersection casts/coercions through a new runtime helper and harden proxy generation against null (bootstrap) classloaders.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/antlr/GroovyParser.g4	Grammar changes: intersection types in cast parens and `coercionType` for `as`/`!instanceof`.
src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java	Builds `IntersectionTypeClassNode`, rejects duplicate intersection components, adjusts `as` and `!instanceof` handling.
src/main/java/org/codehaus/groovy/ast/IntersectionTypeClassNode.java	New `ClassNode` representing user-written intersection cast targets with component ordering + reclassification.
src/main/java/org/codehaus/groovy/control/ResolveVisitor.java	Resolves intersection components and reclassifies class-vs-interface parts post-resolution.
src/main/java/org/codehaus/groovy/transform/stc/StaticTypesMarker.java	Adds markers to carry intersection functional target + marker interfaces through compilation.
src/main/java/org/codehaus/groovy/transform/stc/StaticTypeCheckingVisitor.java	Validates/applies intersection-cast behavior in STC and teaches `checkCast` to decompose intersections.
src/main/java/org/codehaus/groovy/classgen/AsmClassGenerator.java	Emits indy no-op for lambda/methodref intersection casts and invokes runtime helper for other intersection casts/coercions.
src/main/java/org/codehaus/groovy/runtime/IntersectionCastSupport.java	New runtime helper for intersection cast/coercion (`castTo` / `asType`).
src/main/java/org/codehaus/groovy/runtime/ProxyGeneratorAdapter.java	Fixes NPE risk by avoiding storing bootstrap (`null`) classloaders in internal loader lists.
src/main/java/org/codehaus/groovy/classgen/asm/sc/AbstractFunctionalInterfaceWriter.java	Adds marker-aware `altMetafactory` bootstrap argument construction for intersection targets.
src/main/java/org/codehaus/groovy/classgen/asm/sc/StaticTypesLambdaWriter.java	Collects intersection markers and passes them to indy bootstrap for lambdas.
src/main/java/org/codehaus/groovy/classgen/asm/sc/StaticTypesMethodReferenceExpressionWriter.java	Threads intersection markers + serializable flag into method-reference indy generation.
src/main/java/org/codehaus/groovy/classgen/asm/sc/StaticTypesClosureWriter.java	Adds marker interfaces to statically-compiled closure literal classes when safe.
src/spec/doc/core-semantics.adoc	Documents intersection casts/coercion semantics and examples.
src/spec/doc/core-differences-java.adoc	Documents Java-difference: intersection casts on lambdas/method refs and Groovy `as` form.
src/spec/test/CoercionTest.groovy	Adds spec tests/examples for intersection casts/coercion.
src/test/groovy/org/apache/groovy/parser/antlr4/IntersectionCastParserTest.groovy	Parser-level tests ensuring intersection targets become `IntersectionTypeClassNode` and invalid cases error.
src/test/groovy/groovy/transform/stc/IntersectionCastSTCTest.groovy	STC tests for intersection functional target selection, metadata, and validation errors.
src/test/groovy/groovy/lang/IntersectionCastE2ETest.groovy	End-to-end runtime tests for statically compiled intersection lambdas/method references (incl. serialization).
src/test/groovy/groovy/lang/IntersectionCoercionTest.groovy	Runtime tests for dynamic intersection cast/coercion on non-functional sources (Closure/Map/value/null).
src/test/groovy/groovy/lang/IntersectionClosureLiteralTest.groovy	Tests native marker-interface addition for statically compiled closure literals under intersection casts.
src/test/groovy/groovy/util/ProxyGeneratorAdapterTest.groovy	Regression tests for mixing bootstrap + user classloaders in proxy interface lists (GROOVY-11999).

codecov-commenter · 2026-05-06T10:52:24Z

Codecov Report

❌ Patch coverage is 84.87395% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.8457%. Comparing base (200f089) to head (276616f).

Files with missing lines	Patch %	Lines
...sc/StaticTypesMethodReferenceExpressionWriter.java	47.0588%	4 Missing and 5 partials ⚠️
...roovy/transform/stc/StaticTypeCheckingVisitor.java	85.1852%	2 Missing and 6 partials ⚠️
...dehaus/groovy/runtime/IntersectionCastSupport.java	83.3333%	1 Missing and 3 partials ⚠️
...sgen/asm/sc/AbstractFunctionalInterfaceWriter.java	91.1765%	1 Missing and 2 partials ⚠️
...oovy/classgen/asm/sc/StaticTypesClosureWriter.java	80.0000%	0 Missing and 3 partials ⚠️
...roovy/classgen/asm/sc/StaticTypesLambdaWriter.java	78.5714%	0 Missing and 3 partials ⚠️
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	92.3077%	2 Missing ⚠️
...codehaus/groovy/ast/IntersectionTypeClassNode.java	89.4737%	1 Missing and 1 partial ⚠️
...codehaus/groovy/runtime/ProxyGeneratorAdapter.java	60.0000%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2518        +/-   ##
==================================================
+ Coverage     67.8231%   67.8457%   +0.0226%     
- Complexity      32371      32454        +83     
==================================================
  Files            1494       1496         +2     
  Lines          124266     124481       +215     
  Branches        22297      22369        +72     
==================================================
+ Hits            84281      84455       +174     
- Misses          32704      32718        +14     
- Partials         7281       7308        +27

Files with missing lines	Coverage Δ
...rg/codehaus/groovy/classgen/AsmClassGenerator.java	`85.1528% <100.0000%> (+0.2305%)`	⬆️
...va/org/codehaus/groovy/control/ResolveVisitor.java	`90.2948% <100.0000%> (+0.0600%)`	⬆️
...codehaus/groovy/tools/javac/JavaStubGenerator.java	`87.0130% <ø> (ø)`
...odehaus/groovy/transform/RecordBaseASTStubber.java	`84.0909% <ø> (ø)`
...dehaus/groovy/transform/stc/StaticTypesMarker.java	`100.0000% <100.0000%> (ø)`
...g/codehaus/groovy/tools/groovydoc/TagRenderer.java	`72.9904% <ø> (ø)`
...y/tools/groovydoc/antlr4/GroovydocJavaVisitor.java	`70.8029% <ø> (ø)`
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	`86.6155% <92.3077%> (-0.0454%)`	⬇️
...codehaus/groovy/ast/IntersectionTypeClassNode.java	`89.4737% <89.4737%> (ø)`
...codehaus/groovy/runtime/ProxyGeneratorAdapter.java	`89.0792% <60.0000%> (-0.1681%)`	⬇️
... and 6 more

... and 4 files with indirect coverage changes

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Grammar + AST. intersectionType rule, IntersectionTypeClassNode, AstBuilder updates. Includes parser tests; no semantic impact (ResolveVisitor errors out on it).

Resolution + STC. ResolveVisitor resolves components; StaticTypeCheckingVisitor.visitCastExpression validates and propagates. LAMBDA_MARKERS metadata. Static error messages.

Bytecode for lambdas/method refs. writeFunctionalInterfaceIndy markers, altMetafactory flags. Static parity with Java's (R & S) ()->….

as coercion. Closure asType overload, ProxyGenerator plumbing, dynamic castToType(Object, Class[]).

Closure literal native intersection. StaticTypesClosureWriter generates a class implementing all components for (R & S) { -> ... }, docs.

…tstrap and user classloaders

testlens-app · 2026-05-07T10:32:40Z

✅ All tests passed ✅

🏷️ Commit: 276616f
▶️ Tests: 94430 executed
⚪️ Checks: 24/24 completed

Learn more about TestLens at testlens.app.

paulk-asert changed the title ~~Groovy11998~~ GROOVY-11998: Better support of intersection types May 6, 2026

paulk-asert requested a review from Copilot May 6, 2026 10:01

Copilot started reviewing on behalf of paulk-asert May 6, 2026 10:03 View session

Copilot AI reviewed May 6, 2026

View reviewed changes

paulk-asert added 7 commits May 7, 2026 19:30

GROOVY-11998: Better support of intersection types (part 1)

0c319c1

Grammar + AST. intersectionType rule, IntersectionTypeClassNode, AstBuilder updates. Includes parser tests; no semantic impact (ResolveVisitor errors out on it).

GROOVY-11998: Better support of intersection types (part 2)

c3e90f2

Resolution + STC. ResolveVisitor resolves components; StaticTypeCheckingVisitor.visitCastExpression validates and propagates. LAMBDA_MARKERS metadata. Static error messages.

GROOVY-11998: Better support of intersection types (part 3)

b404648

Bytecode for lambdas/method refs. writeFunctionalInterfaceIndy markers, altMetafactory flags. Static parity with Java's (R & S) ()->….

GROOVY-11998: Better support of intersection types (part 4)

6e17715

as coercion. Closure asType overload, ProxyGenerator plumbing, dynamic castToType(Object, Class[]).

GROOVY-11998: Better support of intersection types (part 5)

fb52243

Closure literal native intersection. StaticTypesClosureWriter generates a class implementing all components for (R & S) { -> ... }, docs.

GROOVY-11999: ProxyGeneratorAdapter NPE when proxy interfaces mix boo…

54cb857

…tstrap and user classloaders

GROOVY-11998: Better support of intersection types (copilot review)

276616f

paulk-asert force-pushed the groovy11998 branch from b154bbc to 276616f Compare May 7, 2026 09:33

paulk-asert merged commit a24f1c7 into apache:master May 8, 2026
25 checks passed

paulk-asert deleted the groovy11998 branch May 8, 2026 08:39

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GROOVY-11998: Better support of intersection types#2518

GROOVY-11998: Better support of intersection types#2518
paulk-asert merged 7 commits into
apache:masterfrom
paulk-asert:groovy11998

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Pull request overview

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✅ All tests passed ✅

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codecov-commenter commented May 6, 2026 •

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