[antlr-interest] [fatal] rule Tokens has non-LL(*) decision due to recursive rule invocations

[Gavin Lambert]

At 07:50 7/11/2008, Giovane wrote:
>"Test.g:1:8: [fatal] rule Tokens 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 tried several alternatives in this grammar but I couldn't solve 
>the problem. I have no idea what the rule "Tokens" means, because 
>I don't have this rule in my grammar.

The "Tokens" rule is the auto-generated parent rule of all your 
top-level lexer rules.  So this means that there is ambiguity 
between these rules.

The most obvious problem I can see is the PATHTERM rule.  Since it 
refers to other non-fragment lexer rules (especially on the left 
side), that's instant ambiguity right there.

I think the biggest problem though is that many of the lexer rules 
you have there (eg. the expressions and operators) look like they 
ought to be parser rules instead.  Certainly, if you want to keep 
them as lexer rules then you'll need to modify them for 
whitespace.

I'm not sure why you're getting that specific error, but it's 
probably not helped by your grammar being completely saturated 
with ambiguity (StepExpr is also internally ambiguous).