Throw warning if symbol conflicts with generated code in another language or runtime

[KvanTTT]

Consider grammar with file root element. If generate parser for Python2 target the following error will be thrown:

error(134): L.g4:18:0: symbol file conflicts with generated code in target language or runtime

But if we change runtime to Java no error and warning will be thrown.

So, I suggest to throw a warning in this case:

warning(134): L.g4:18:0: symbol file conflicts with generated code in another language or runtime

This check allows us to write more universal grammars for all targets.

[mike-lischke]

Hmm, but then you might get warnings for names that you don't care for, if you don't intent to use a grammar in another language. That doesn't play well with build systems that strive for zero error and warning messages.

[KvanTTT]

Maybe ANTLR should have a command line parameter universal that point on whether grammar should be wide or not? The user from this issue antlr/grammars-v4#568 suffers from runtime keywords.

[mike-lischke]

How can this work out? You would need to test for all supported languages and as soon as a new language comes up you have to update that. That's this kind of cleverness which gets in the way more than what it solves. If a grammar is not compatible with a target language it must be changed, as easy as that.

[parrt]

I think most people use a single target and so I think we are okay. Closing.