[antlr-interest] executing actions while recovering from syntaxerrors

[Don Caton]

Ter:

I generally need to guard actions anyhow, to prevent null pointer exceptions
when a rule doesn't successfully match.  So automatic guarding would be
beneficial and simplify action code, at least for me.  I'd love to eliminate
the repetitious "if (#x != NULL )" tests I have all over the place.

However, there may be cases where you'd always want to run an action.
Perhaps an option to suppress guarding in that case:

  { options { guarded = false; } : <action code> }

This would also serve to self-document the fact that the action always runs,
even if the rule fails.  You could also have a global option to turn it on
or off for the whole grammar, to maintain compatibility with existing
grammar and satisfy everyone's personal preference.

Don
 
> Anyway, putting a guard around every action looks gross and 
> takes time/space (oh, and I guess is no guarantee it's safe):
> 
> if ( !recoveryMode ) { action }
> 
> Anybody wanna comment?  For now, the actions are unguarded.
> 
> Ter
> --
> CS Professor & Grad Director, University of San Francisco 
> Creator, ANTLR Parser Generator, http://www.antlr.org 
> Cofounder, http://www.jguru.com
> 
> 
> 
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