validation - ANTLR-based rule engine in java -

i writing antlrv4 grammar implement simple rule engine parse fix messages, , specify action taken when rule violated.

this grammar stands:

    grammar ruledefinition;  ruleset: rule+;  rule :  'tag(' int ')' numberop (int | float| string) (action_director action)?;  id      :   [a-za-z]+ ;        // match identifiers int     :   [0-9]+;            // match integers float   :   '0'..'9'+('.'('0'..'9')*)? ;            // match float newline :'\r'? '\n' ;           // return newlines parser (end-statement signal) ws     : [ \t\n\r]+ -> skip ;   // toss out whitespace number_op      :   eq|gr|ge|ls|le|ne; numberop       :   eq|gr|ge|ls|le|ne; eq      :   '='; gr: '>'; ge: '>='; ls: '<'; le: '<='; ne: '!='; action_director : '->'; action: 'warn' | 'error'; string : '"' (' '..'~')* '"'; 

the problem generated code unable correctly parse when rule contains action_director (->), error "mismatched input 'error' expecting action"

parsing successful for:

tag(9)>0 

parsing fails for:

tag(9)>0 -> error 

any pointers on how correct above highly appreciated.

look @ 3 lines:

warn: 'warn'; error: 'error'; action: warn|error; 

these lexer rules (upper case start character). lexer responsible split input tokens of determined type. 'error' can have 1 token type , antlr decides error (two rules error , action match, , erroris first defined).

to resolve transform lexer rules parser rules (lower case start character):

rule :  'tag' '(' int ')' numberop (int | float| string) (action_director action)*;  ....  action : warn | error; numberop :   eq|gr|ge|ls|le|ne; stringop :   eq|ne;  ... 

parser rules compose tokens instead of joining them. means action can warn or error.