[antlr-interest] Bug or badly written error case

[Benjamin Shropshire]

I have run into a case where some antler generated code goes into an 
error state but gives little or no helpful information. The error was 
cause by having these two rules in the same grammar:

WS        :    (' '|'\t')+ {Skip();} ;

import
    : 'import' (' ' | '\t')+ FText eol_     -> ^(IMPORT FText)
    ;

the error was removed by changeling this to

WS        :    (' '|'\t')+ {Skip();} ;

import
    : 'import' WS FText eol_     -> ^(IMPORT FText)
    ;

This error in my code seems to be exposing a bug (or what looks like 
one) in antlr because it causes some of the C# antlr runtime to throw a 
RewriteEmptyStreamException. This gives no useful information (with 
regards to finding my error) and seems like it exposes to much of the 
underlying runtime.

I hope this is useful.

--Benjamin Shropshire