[antlr-interest] error(211)

[Gavin Lambert]

At 20:39 6/08/2007, Martin Kohl wrote:
>I've stumbled upon an error:
>error(211): Expr.g:490:3: [fatal] rule rule_name has non-LL(*) 
>decision due to recursive rule invocations reachable from alts 
>1,4.  Resolve by left-factoring or using syntactic predicates or 
>using backtrack=true option.
>
>I've had this error in a few other places and I resolved it by 
>setting the backtrack=true option. However this doesn't work for 
>this rule:
>         (    expression ','
>         |    '*' ','
>         |    ','
>         )*
>         expression ':'
>
>The Line Reference of the error message points to the second 
>expression. If I remove the * or the second expression the error 
>is resolved.

I'm assuming that this fragment is part of the 'expression' rule, 
or that the expression rule either directly or indirectly contains 
whichever rule that is.

It's hard to give you anything specific without seeing more of the 
grammar, but basically you need to make sure that your rules 
aren't left-recursive -- ie. that there's always at least one 
token to consume in each recursive "loop", and thus the loop 
becomes bounded instead of infinite.