[antlr-interest] Syntactic predicates vs branch-local declarations.

[Monty Zukowski]

Below your code block is an action, not a declaration.  All actions
are wrapped in if(guessing) so that syntactic predicates work.  This
is not a bug.  There is no such thing as a branch-local declaration in
antlr 2.

 a: { int v1, v2; } A  v1 = b  v2 = b;

Monty

On 07 Dec 2006 21:32:51 -0500, r. clayton <rvclayton at acm.org> wrote:
> Antlr 2.7.7 is generating bad code for grammars using both syntactic predicates
> and branch-local declarations, as in
>
>   a: { int v1, v2; } A  v1 = b  v2 = b;
>
>   c: (d) => d | e;
>
> Part of the code generated is
>
>   if ( inputState.guessing==0 ) {
>     int v1, v2;
>     }
>   match(A);
>   v1=b();
>   v2=b();
>
> which doesn't compile because v1 and v2 can't escape their scope.  The fix is
> to make the branch-local declarations rule local:
>
>   a { int v1, v2; } : A  v1 = b  v2 = b;
>
>
>
>
>
>
>