Further investigation confirms that this does seem to crop up quite a bit, which suggests I'm definitely doing something wrong. I'm just hoping that someone might be able to suggest a different way to do what I need to do (i.e. insert an imaginary token in place of the optional one if it's not specified)?
Thanks, Ross On Sun, Oct 16, 2011 at 11:53 PM, Maximilien Colange <[email protected]>wrote: > It appears that this "bug" is frequently reported. > It would be nice if ANTLR raised an error (or a warning) when a token is > given a reference in a syntactic predicate. > > However, I do not know whether it is easy to detect. I already > encountered this problem, and it occured in a "hidden" ANTLR-generated > syntactic predicate. I am afraid the error is difficult to detect in > such cases. > > And just for curiosity, why is not it possible to reference local > variables or to assign from token in a syntactic predicate ? > > -- > Maximilien > > Le 10/15/11 11:34 PM, Jim Idle a écrit : > > Your problem does not look to be the rewrite rule, but the fact that you > > are referencing a local variable in a predicate, or have tried to assign > > from a token in a predicate. > > > > Look for something like this > > > > ((id=IDENTIFIER)=> id=IDENTIFIER)? .... > > > > > > But regardless, this is the rewrite rule that is the problem as far as I > > can see. Try commenting it out for instance. > > > > Jim > > > >> -----Original Message----- > >> From: [email protected] [mailto:antlr-interest- > >> [email protected]] On Behalf Of Ross Bamford > >> Sent: Saturday, October 15, 2011 5:40 AM > >> To: [email protected] > >> Subject: [antlr-interest] Rewrite action causing error in parser? > >> > >> Hi all, > >> > >> I have a grammar I'm currently working on (posted in another thread the > >> other day), which has the following rule: > >> > >> meth_call_expr > >> : (id = IDENTIFIER DOT)? func_call_expr -> ^(METHOD_CALL { > >> ($id==null) ? > >> adaptor.create(SELF, "SELF") : adaptor.create(IDENTIFIER, > >> $id.getText()) } > >> func_call_expr) > >> ; > >> > >> As you can see, I'm using an action in the rewrite rule to insert > >> either the > >> (optional) IDENTIFIER, or an imaginary SELF node if IDENTIFIER is not > >> specified. The problem I'm having is that this generates a parser that > >> won't compile. Specifically, it generates the following bit of code > >> (edited by hand for brevity and to highlight the error): > >> > >> /* **** [ CODE ] **** */ > >> // $ANTLR start synpred6_BasicLang > >> public final void synpred6_BasicLang_fragment() throws > >> RecognitionException { > >> > >> Token =null; //<-- ERROR HERE > >> > >> /* ... later on ... */ > >> > >> switch (alt23) { > >> case 1 : > >> // > >> C:\\Users\\chantelle\\workspace\\basiclang\\src\\com\\roscopeco\\basicl > >> ang\\parser\\BasicLang.g:99:8: > >> id= IDENTIFIER DOT > >> { > >> > >> id=(Token)match(input,IDENTIFIER,FOLLOW_IDENTIFIER_in_synpred6_BasicLan > >> g232); > >> if (state.failed) return ; //<-- AND HERE > >> > >> match(input,DOT,FOLLOW_DOT_in_synpred6_BasicLang234); > >> if > >> (state.failed) return ; > >> > >> } > >> break; > >> > >> } > >> /* **** [ END ] **** */ > >> > >> Obviously the problem is the "Token =null" line, which should be "Token > >> id = null". Changing it by hand fixes the errors and makes the parser > >> work as expected. > >> > >> So I have two questions - is this the right way to go about inserting > >> an imaginary token if an optional token isn't in the input, and if so, > >> what am I doing wrong to cause the error above? > >> > >> Thanks in advance, > >> Ross > >> > >> List: http://www.antlr.org/mailman/listinfo/antlr-interest > >> Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your- > >> email-address > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
