[antlr-interest] revised subject: tree matcher problem with validating semantic predicate

[Gavin Lambert]

At 09:34 6/08/2009, Tom Smith wrote:
 >I have narrowed down my problem.  The validating semantic
 >predicate properly throws a FailedPredicateException in
 >a regular tree grammar, but does not when filter=true.
[...]
 >Am I wrong to expect this?

I've never really played with filter=true in tree grammars, but 
when used in lexers the whole point is to only define the rules 
you care about and anything that doesn't successfully match a rule 
is ignored.

Thus if the predicate fails, it's not an error -- it's simply not 
a match for that rule, and the parser will go try another 
alternative, or give up and skip it.

So I'm not surprised that the exception isn't being produced.