[antlr-interest] Identical characters cause error

[Ngọc Minh Lê]

This simplistic grammar can't be compiled:

grammar T;

x    :    '\u006c';
y    :    '\u006C';
z    :    'l';

ANTLR reports this error:

The following token definitions can never be matched because prior tokens
match the same input: T__5,T__6

In my grammar, by accident I had both ASCII character and Unicode escaped
character and it took me hours to figure out the problem. I think ANTLR
should recognize those are the same character before creating tokens for
them to avoid this error.

Best wishes,
Minh.

-- 
Lê Ngọc Minh
Hanoi University of Science and Technology, Computer Science
Skype: ngocminh_oss | Yahoo: ngocminh_oss | Tel: +84 988 456 037