ANTLR Ambiguity Issue

问题

I have this grammar.

grammar MyGrammar;
prog : lexeme* ;

lexeme :
TOK_INTLIT  : [0-9]+;
Identifiers  : Letter (Letter | Digit | '_' )* ;
fragment Letter     : [a-zA-Z] ;
fragment Digit      : [0-9] ;
...

Now when I input this: int 2x = 20;

I am expecting an error for identifier but I am getting an output like this:

Type = TOK_INT value = [int] Line 1, Column 0,
Type = TOK_INTLIT value = [2] Line 1, Column 4,
Type = Identifiers value = [x] Line 1, Column 5,

2x is being split. Am I doing something wrong or is there a way to fix such things?

来源：https://stackoverflow.com/questions/28661601/antlr-ambiguity-issue