[antlr-interest] Bug with predicates and DFAs? (ANTLR 3.0)

[Braun, Kevin T]

Hi,

I tried using this rule:

keywordSet

            :           {setCanBeId &&
input.LT(1).getText().equals("set")}? IDENT;

 

in order to allow "set" to appear either as a keyword or as an
identifier.  The rule where keywordSet is used ends up being involved in
an LL(*) decision.  In the generated parser, the code in the DFA has a
method specialStateTransition declared as:

public int specialStateTransition(int s, IntStream input) throws
NoViableAltException

 

The predicate from keywordSet ends up in this specialStateTransition
method (I guess that's the predicate hoisting), but this results in
invalid code: inside this method, input is an IntStream and
IntStream.LT() returns an int, not a token object.  That makes
input.LT(1).getText() invalid.

 

Regards,

Kevin

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