[SOLVED] How to make antlr find invalid input throw exception

How to make antlr find invalid input throw exception

I have the following grammar:

grammar Expr;


expr : '-' expr                                       # unaryOpExpr
     | expr ('*'|'/'|'%') expr                        # mulDivModuloExpr
     | expr ('+'|'-') expr                            # addSubExpr
     | '(' expr ')'                                   # nestedExpr
     | IDENTIFIER '(' fnArgs? ')'                     # functionExpr
     | IDENTIFIER                                     # identifierExpr
     | DOUBLE                                         # doubleExpr
     | LONG                                           # longExpr
     | STRING                                         # string
     ;


fnArgs : expr (',' expr)*                             # functionArgs
       ;

IDENTIFIER : [_$a-zA-Z][_$a-zA-Z0-9]* | '"' (ESC | ~ ["\\])* '"';
LONG : [0-9]+;
DOUBLE : [0-9]+ '.' [0-9]*;
WS : [ \t\r\n]+ -> skip ;

STRING: '"' (~["\\\r\n] | ESC)* '"';

fragment ESC : '\\' (['"\\/bfnrt] | UNICODE) ;
fragment UNICODE : 'u' HEX HEX HEX HEX ;
fragment HEX : [0-9a-fA-F] ;

MINUS : '-' ;
MUL : '*' ;
DIV : '/' ;
MODULO : '%' ;
PLUS : '+' ;

// math function
MAX: 'MAX';

when I enter following text,It should be effective

-1.1

bug when i enter following text:

-1.1ffff

I think it should report an error, bug antlr didn't do it, antlr captures the previous "-1.1", discard "ffff", but i want to change this behavior, didn't discard invalid token, but throw exception,report detection invalid token.

So what should i do, Thanks for your advice

Solution

Are you using expr as your main rule? if so make another rule, call it something like parse or program and simply write it like this:

parse: expr EOF;

This will make antlr not ignore trailing tokens that don't make sense, and actually throw an error.