Hi Terence,
>> The reason is that the empty production has no rewrite. However, in
>> ANTLR 3.0.1, this error did not happen.
>>
>> So, my question is: is this is a bug, or intentional behaviour? I
>
> hi!
>
> It is proper behavior; if there is no listBody then list must indicate
> there is an error.
Just to be clear here --- you're saying this behaviour exhibited in
ANTLR 3.0.1 was entirely broken? It was actually quite a useful
behaviour. For example, in the Java 1.5 Grammar you have:
> classDeclaration
> : 'class' Identifier (typeParameters)?
> ('extends' type)?
> ('implements' typeList)?
> classBody
> ;
>
> ...
>
> classBody
> : '{' classBodyDeclaration* '}'
> ;
>
> ...
>
> classBodyDeclaration
> : ';'
> | ... [other productions]
> ;
In my ideal AST, the tokens ';', '{' and '}' are not present. But, to
use the rewrite rules with this, I have to provide extra tokens like so:
> classBody
> : '{' classBodyDeclaration* '}' -> (^X classBodyDeclaration*)
> ;
>
> ...
>
> classBodyDeclaration
> : ';' -> (^Y)
> | ... [other productions]
> ;
This seems clumsy, since neither the X or Y tokens are actually needed
in my final AST. With ANTLR 3.0.1 I just left them as empty
productions, and it worked really nicely.
One solution I guess is to refactor the grammar, by inlining the
productions in question. So instead of the above, after one iteration
we get:
> classDeclaration
> : 'class' Identifier (typeParameters)?
> ('extends' type)?
> ('implements' typeList)?
> '{' classBodyDeclaration* '}'
> -> ^(CLASS ...)
> ;
But, I still need to inline classBodyDeclaration ... and as I do all
this the neatness of the original grammar is being lost.
Any suggestions? Did I miss anything?
Cheers,
Dave
> Ter
--
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Victoria University of Wellington,
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