[antlr-interest] Tree parser tree building bug and workaround

[Monty Zukowski]

On 11/29/06, Micheal J <open.zone at virgin.net> wrote:
> Hi Monty,
>
> > I just found a bug in 2.7.7 (and 2.7.4).  I have a tree
> > parser rule that builds a tree (just adding a new parent
> > node), like this:
> >
> > rule1:
> > #( T1 T2 T3
> >   { ##=#(#[NEWROOT],##); }
> >   )
> >   ;
>
> Shouldn't that be:
>
> Rule1
>   :  #( T1 T2 T3
>      )
>      { ##=#(#[NEWROOT],##); }
>   ;
>
> With the action block following the tree pattern matching specification.
>
> > >From inside the action, I see that the tree is built properly.  But
> > for some reason, upon exit of the rule the AST for rule1 is
> > replaced by the original.  (You can see it in the generated code).
>
> This resonates with my preposition that action block placement might be the
> issue here.
>

I suppose that is it, but I don't understand why.  What does it
matter?  I would expect the root to be built after T1 has been
matched.  Why can't I manipulate it from inside the #() ?

Monty

Monty