[antlr-interest] Confusing, hopefully-final, problems

[Sam Barnett-Cormack]

Hi all

So, I solved the recursion issue (which had been complicated by me 
failing to notice a '|' in the standard), and fixed a lot of intractable 
issues using predicates (or backtracking, at least for now). However, 
I'm still getting some errors/warnings which I can't for the life of me 
figure out the reason for. I know what they mean, but they don't make 
sense. The grammar is, of course, attached. The build errors I'm getting 
are:

[18:09:42] warning(200): ASN_1.g:346:108: Decision can match input such 
as "'('" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] warning(200): ASN_1.g:470:4: Decision can match input such as 
"'...'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] warning(200): ASN_1.g:473:31: Decision can match input such 
as "'}'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] warning(200): ASN_1.g:473:31: Decision can match input such 
as "','" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] warning(200): ASN_1.g:473:31: Decision can match input such 
as "EOF" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] error(201): ASN_1.g:473:31: The following alternatives can 
never be matched: 2

[18:09:42] warning(200): ASN_1.g:518:15: Decision can match input such 
as "'...'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[18:09:42] error(201): ASN_1.g:518:15: The following alternatives can 
never be matched: 2


In the case of line 473, some of those inputs that can supposedly be 
matched in more than one way can't really be matched at all, as far as I 
can tell. In the other cases, the inputs can be matched, but I'm pretty 
sure they can't be matched by the things it says they can be.

I'm sure that this isn't some sort of software bug, because I know antlr 
isn't that flaky and weird. Beginning to feel incredibly stupid, but can 
anyone offer me any tips or ideas, or even a full debugging of my code 
(hey, it's unlikely, but I can hope, right)?

Thanks all

Sam