[antlr-interest] Bug? Invalid Java code generated

[Andreas Meyer]

Sam Barnett-Cormack schrieb:
> Hi all
>
> The attached grammar (which you're probably all tired of) generates 
> Java code with an error in. I've checked, and the error isn't in a 
> copy action or predicate - it's in the expansion of $text in a parser 
> predicate. I don't know if I've used $text incorrectly, because I'm 
> using it as I understand the documentation says to (including the 
> ANTLR book).
>
> The error is:
>
> retval cannot be resolved
>
> on: ASN_1Parser.java
> line: line 17279
>
> The generated function in question is:
>
> // $ANTLR start synpred26_ASN_1
>     public final void synpred26_ASN_1_fragment() throws 
> RecognitionException {
>         // /home/sdb/workspace/asn.1-parse/grammars/ASN_1.g:583:44: ( 
> nameForm {...}?)
>         // /home/sdb/workspace/asn.1-parse/grammars/ASN_1.g:583:44: 
> nameForm {...}?
>         {
>         pushFollow(FOLLOW_nameForm_in_synpred26_ASN_13890);
>         nameForm();
>
>         state._fsp--;
>         if (state.failed) return ;
>         if ( 
> !((isStandardOIDName(input.toString(retval.start,input.LT(-1))))) ) {
>             if (state.backtracking>0) {state.failed=true; return ;}
>             throw new FailedPredicateException(input, 
> "synpred26_ASN_1", "isStandardOIDName($text)");
>         }
>
>         }
>     }
> // $ANTLR end synpred26_ASN_1
>
> The rule from the grammar (whole thing attached) is:
>
> objIdComponents options{backtrack=true;} : nameForm 
> {isStandardOIDName($text)}? | numberForm | nameAndNumberForm | 
> definedValue ;
>
> If this isn't a bug, can someone explain how to pass a function called 
> in a predicate the text matched so far? If this is a bug, anyone have 
> a workaround? Please. Thanks!

I'm currently not 100% sure of the exact syntax, but why dont you use 
something like $nameForm.text ? This is the simplest workaround for the 
problem you showed. Or do you have other cases where you need to easily 
access the $text of a lot of rules?

Andreas