[Patterns][Unnamed] VerifyError with unnamed pattern variable in instanceof

[srikanth-sankaran]

[Patterns][Unnamed] VerifyError with unnamed pattern variable in instanceof

[srikanth-sankaran]

This is exposed by - not caused by - a recent commit #2016

Underlying defective change was introduced via commit b4875fc made for #1517 and merged on 2024-01-29 at 09:51:08

Basically, this commit changed the method org.eclipse.jdt.internal.compiler.ast.TypePattern.bindingsWhenTrue() from being:

	@Override
	public LocalVariableBinding[] bindingsWhenTrue() {
		return this.local != null && this.local.binding != null ?
						new LocalVariableBinding[] { this.local.binding } : NO_VARIABLES;
	}

to

	@Override
	public LocalVariableBinding[] bindingsWhenTrue() {
		return this.local != null && this.local.binding != null && !this.local.isUnnamed(this.local.binding.declaringScope) ?
						new LocalVariableBinding[] { this.local.binding } : NO_VARIABLES;
	}

This is incorrect and was masked so far by the fact that we wouldn't even deconstruct the record pattern in this scenario till
#1517

Now since the unnamed pattern binding is not returned as being live, its live range in the region corresponding to "thunk" emitted by org.eclipse.jdt.internal.compiler.ast.InstanceOfExpression.generateCode(BlockScope, CodeStream, boolean) is not closed by this chunk of code:

eclipse.jdt.core/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/InstanceOfExpression.java

Lines 136 to 141 in a9231ed

	falseLabel.place();
	for (LocalVariableBinding binding : this.pattern.bindingsWhenTrue()) {
	binding.recordInitializationEndPC(codeStream.position);
	}
	codeStream.iconst_0();
	continueLabel.place();

thereby leaving the stackmap inconsistent.

Interestingly, I had already found and fixed this problem in my private branch where I am accumulative fixes to be merged in after 4.32 master opens:

https://github.com/srikanth-sankaran/eclipse.jdt.core/blob/8bea15fd0c0cc98b2f2f8a5080e8ec87806f9207/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java#L48-L51