False positive in grammar multiple assignments validation

[cdietrich]

Langium version: 3.3

given the grammar

entry Model:
    expr=Expression;

Expression: Equality;

Equality infers Expression:
    Literal (({infer Equals.left=current} '==' | {infer NotEquals.left=current} '!=')  right=Literal)*;

Literal: value=INT;

the validator complains about

src/language/hello-world.langium:9:88 - Found multiple assignments to 'right' with the '=' assignment operator. Consider using '+=' instead to prevent data loss.

imho this is a false positive with the ast rewrite. maybe it is not properly detected if happing on all branches of an alternative.

[cdietrich]

cc @JohannesMeierSE

[JohannesMeierSE]

@cdietrich thanks for the bug report! I will investigate it, but I will need to find some free time for that. Is it urgent on your side?

with the ast rewrite. maybe it is not properly detected if happing on all branches of an alternative

I agree: ( ... right=Literal )* looks critical for the validation. A check for creating new objects inside ( ... )* is probably the solution.

[JohannesMeierSE]

@cdietrich I investigated the issue and created the PR #1766 for it: Rewrite actions were checked in general, but not all combinations of looped and nested rewrite actions.