Stub compilation causes harmful AST changes

labels on implicit returns? I guess you mean that returns are added. As they don't exist before, they can't have a label. Of course if the last statement is labeled, then the return needs to get that label.

I think switching the addition of implicit returns off is a good idea

I mean that Verifier doesn't copy the label when it inserts an implicit return. This might not be a problem if Verifier runs in phase class generation, but it is a problem (at least for my transforms) if Verifier runs in phase conversion.

Yes, it would be a good idea to switch off everything that modifies the AST.

it does not copy the label... hmm.. that is possibly a bug... As for not modifying the AST, that is a bit difficult. You see if the AST is not modified, then Verifier would not have to be run. What verifier needs to do is adding the methods for GroovyObject, adding methods for properties and such stuff. Normally it would also add covariants, but that is disabled.

But maybe it is time to split out the things we want verifier do for stubs into another class and then call that one from Verifier and from the stub generator instead.

Rev. 16562/63 provides a partial fix - Verifier now retains a label when promoting an ExpressionStatement to an implicit ReturnStatement. However, the general problem that several AST changes (e.g. addition of implicit returns) occur in phase conversion instead of class generation if joint compilation is on, remains unsolved. This can make it difficult to write reliable AST transformations.

Rev. 16587/88 provides another partial fix - implicit returns are no longer added during stub generation in phase conversion, but always in phase class generation. Several other AST modifications are still done during stub generation although they wouldn't have to be done at such an early stage.