[antlr-interest] Inexplicable RewriteEmptyStreamException in parser grammar

[Richard Thrippleton]

False alarm. There was some subtle abuse going on deep down in our setup of 
the parser (our tree adaptor was creating error nodes incorrectly). Apologies!

Richard

Richard Thrippleton wrote:
> I'm using the Java target with ANTLR 3.2, and having a problem in a rule in my parser grammar that looks like this:
> 
> "variableInit [ String name ]
>   : ASSIGNMENT id=initializer
>     -> ^(ASSIGNMENT IDENTIFIER[$ASSIGNMENT, $name] initializer)"
> 
> In a particular case where the 'initializer' rule fails to match and issues a syntax error, I'm getting a RewriteEmptyStreamException that cites "rule initializer" popping up from a line that looks like this:
> 
> "// 1151:5: -> ^( ASSIGNMENT IDENTIFIER[$ASSIGNMENT, $name] initializer )
> {
>   {
>     CommonTree root_1 = (CommonTree)adaptor.nil();
>     root_1 = (CommonTree)adaptor.becomeRoot(stream_ASSIGNMENT.nextNode(), root_1);
>     adaptor.addChild(root_1, (CommonTree)adaptor.create(IDENTIFIER, ASSIGNMENT179, name));
>     adaptor.addChild(root_1, stream_initializer.nextTree());           <-------------------- ****This line****
>     adaptor.addChild(root_0, root_1);
>   }
> }"
> 
> In terms of error handling we're just using the default recovery (not overriding it with 'catch'/'rulecatch'). We've overridden reportError to pretty-print the RecognitionExceptions, but that's about it. Should I be needing to do anything special to cope with parsing failures of subrules, or should the default be sufficient to prevent these exceptions? Otherwise, where is the problem likely to lie - a defect elsewhere in my grammar, or in ANTLR?
> 
> Cheers,
> Richard
> 
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