ANTLR single grammar input mismatch - antlr4

Question

So far I've been testing with ANTLR4, I've tested with this single grammar:
grammar LivingDSLParser;
options{
language = Java;
//tokenVocab = LivingDSLLexer;
}
living
: query #QUERY
;
query
: K_QUERY entity K_WITH expr
;
entity
: STAR #ALL
| D_FUAS #FUAS
| D_RESOURCES #RESOURCES
;
field
: ((D_FIELD | D_PROPERTY | D_METAINFO) DOT)? IDENTIFIER
| STAR
;
expr
: field
| expr ( '*' | '/' | '%' ) expr
| expr ( '+' | '-' ) expr
| expr ( '<<' | '>>' | '&' | '|' ) expr
| expr ( '<' | '<=' | '>' | '>=' ) expr
| expr ( '=' | '==' | '!=' | '<>' ) expr
| expr K_AND expr
| expr K_OR expr
;
IDENTIFIER
: [a-zA-Z_] [a-zA-Z_0-9]* // TODO check: needs more chars in set
;
NUMERIC_LITERAL
: DIGIT+ ( '.' DIGIT* )? ( E [-+]? DIGIT+ )?
| '.' DIGIT+ ( E [-+]? DIGIT+ )?
;
STRING_LITERAL
: '\'' ( ~'\'' | '\'\'' )* '\''
;
K_QUERY : Q U E R Y;
K_WITH: W I T H;
K_OR: O R;
K_AND: A N D;
D_FUAS : F U A S;
D_RESOURCES : R E S O U R C E S;
D_METAINFO: M E T A I N F O;
D_PROPERTY: P R O P E R T Y;
D_FIELD: F I E L D;
STAR : '*';
PLUS : '+';
MINUS : '-';
PIPE2 : '||';
DIV : '/';
MOD : '%';
LT2 : '<<';
GT2 : '>>';
AMP : '&';
PIPE : '|';
LT : '<';
LT_EQ : '<=';
GT : '>';
GT_EQ : '>=';
EQ : '==';
NOT_EQ1 : '!=';
NOT_EQ2 : '<>';
OPEN_PAR : '(';
CLOSE_PAR : ')';
SCOL : ';';
DOT : '.';
SPACES
: [ \u000B\t\r\n] -> channel(HIDDEN)
;
fragment DIGIT : [0-9];
fragment A : [aA];
fragment B : [bB];
fragment C : [cC];
fragment D : [dD];
//so on...
As far I've been able to figure out, when I write some input like this:
query fuas with field.xxx == property.yyy
, it should match.
However I recive this message:
LivingDSLParser::living:1:0: mismatched input 'query' expecting K_QUERY
I have no idea where's the problem and neither what this message means.

Answer 1

Whenever ANTLR can match 2 or more rules to some input, it chooses the first rule. Since both IDENTIFIER and K_QUERY match the input "query"
, and IDENTIFIER is defined before K_QUERY, IDENTIFIER is matched.
Solution: move your IDENTIFIER rule below your keyword definitions.