[antlr-interest] semantic predicate problem

[Lloyd Dupont]

I'm trying to resolve my problem with this ID which "could be" keyword, by doing a semantic predicate in a parser rule.
something like that:

someStruct
    : something (structWithContextualKeyword)? somethingElse

structWithContextualKeyword
    :    A_KEYWORD
    |    AN_OTHER_KEYWORD
    |    aSpecialId
    ;

aSpecialID
    :    {  isSpecialID(LT(1).getText()) } ?
            t:ID { t.setType(SPECIAL_ID); }
    ;

but this bring me plenty of parsing time error with a stack trace pointing to aSpecialID,
so I tried something like that:
aSpecialID
    :    { isSpecialID(LT(1).getText()) } ?
            t:ID { t.setType(SPECIAL_ID); }
        |
    ;

but this cause the program to hang (no output, no token consume, ..)
so...
any idea?
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