[antlr-interest] syntactic predicates and Kleene star...

[Alan Lehotsky]

In retrospect, this is probably obvious, but maybe someone else is puzzling over this situation.

I have a SQL grammar with a rule

  dotted_name :
         ID ( DOT^ ID)*
  ;

which works correctly, but ANTLR produced the error message

warning(200): plsql.g:1014:8: Decision can match input such as "DOT ID" using multiple alternatives: 1,2
As a result, alternative(s) 2 were disabled for that input

I tried following the advice of using a syntactic predicate, changing the rule to

         ID (DOT)=>(DOT^ ID)*

but that didn't stifle the warning.  I finally realized that I wanted zero-or-more predicted DOT ID's, and rewrote it as

         ID ( (DOT)=>(DOT ^ ID ))*

and the warning went away.