[antlr-interest] automatically generated syntatic predicates become semantic predicates (fragments) plus arguments generate parser which doesn't compile

[Doucette, Charles]

I forgot to mention that this fails to work on both the newest version of ANTLRworks 1.2 plus the previous version (1.1.7?).
I believe ANTLRworks 1.2 is bundled with ANTLR 3.1 - but I am not sure.

Chuck

________________________________
From: Doucette, Charles
Sent: Monday, September 15, 2008 9:53 PM
To: Antlr
Subject: automatically generated syntatic predicates become semantic predicates (fragments) plus arguments generate parser which doesn't compile

Many of my grammar rules have arguments.
Very few of my productions use explicit syntactic predicates or semantic predicates.
Almost all of them seem to generate implicit syntactic/semantic predicates (except the last production of each rule).

Here's the one that is giving me trouble:

dataObjectBodyElement[DataObjectDeclaration dataObj]
            // technically we only allow one trigger definition per file -
            // but let's not limit them in the grammar because that would
            // predefine an order (i.e. trigger always at the beginning or always at the end)
            @init{
                        SubTypeDeclaration stDecl = dataObj;
            }
            :(TRIGGER)=>tr=trigger
                        {
                                    if (tr != null) {
                                                dataObj.getBody().addStatement(tr);
                                    }
                        }
            | commonObjectBodyElement[dataObj]
            |  fieldDeclarations[stDecl]
            ;

In the method dataObjectBodyElement, the generated code looks great, and it gets the argument to pass to that rule from the argument to this rule.

When I look at this rule in ANTLRworks, it says that the production for commonObjectBodyElement corresponds to the semantic predicate {synpred20_vscript}?.

That generated code looks like this:

    // $ANTLR start synpred20_vscript
    public final void synpred20_vscript_fragment() throws RecognitionException {
        // C:\\software\\trunk\\vsw\\source\\com\\vaultus\\studio\\vscript\\parser\\antlr\\vscript.g:501:4: ( commonObjectBodyElement[dataObj] )
        // C:\\software\\trunk\\vsw\\source\\com\\vaultus\\studio\\vscript\\parser\\antlr\\vscript.g:501:4: commonObjectBodyElement[dataObj]
        {
        pushFollow(FOLLOW_commonObjectBodyElement_in_synpred20_vscript1392);
        commonObjectBodyElement(dataObj);

        state._fsp--;
        if (state.failed) return ;

        }
    }
    // $ANTLR end synpred20_vscript

This obviously doesn't compile since it refers to an argument of a parent rule (which is not part of the current context).

Is this an ANTLR bug or a user bug?

In any case, how can I refactor my grammar to avoid this situation (and generate a parser which will compile)?

For the record, here is the rule for commonObjectBodyElement:

commonObjectBodyElement[DataObjectDeclaration dataObj]
            : dom=dataObjectNamedMethod
                        {
                                    if (dom != null) {
                                                dataObj.getBody().addStatement(dom);
                                    }
                        }
            | idx=index
                        {
                                    if (idx != null) {
                                                dataObj.getBody().addStatement(idx);
                                    }
                        }
            ;


Thanks,
Chuck

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