ANTLR4 Token is not recognized when substituted - antlr

Question

I try to modify the grammar of the sqlite syntax (I'm interested in a variant of the where clause only) and I'm keep having a weird error when substituting AND to it's own token.
grammar wtfql;
/*
SQLite understands the following binary operators, in order from highest to
lowest precedence:
||
* / %
+ -
<< >> & |
< <= > >=
= != <> IS IS NOT IN LIKE GLOB MATCH REGEXP
AND
OR
*/
start : expr EOF?;
expr
: literal_value
//BIND_PARAMETER
| ( table_name '.' )? column_name
| unary_operator expr
| expr '||' expr
| expr ( '*' | '/' | '%' ) expr
| expr ( '+' | '-' ) expr
| expr ( '<' | '<=' | '>' | '>=' ) expr
| expr ( '=' | '<>' | K_IN ) expr
| expr K_AND expr
| expr K_OR expr
| function_name '(' ( expr ( ',' expr )* )? ')'
| '(' expr ')'
| expr K_NOT expr
| expr ( K_NOT K_NULL )
| expr K_NOT? K_IN ( '(' ( expr ( ',' expr )* ) ')' )
;
unary_operator
: '-'
| '+'
| K_NOT
;
literal_value
: NUMERIC_LITERAL
| STRING_LITERAL
| K_NULL
;
function_name
: IDENTIFIER
;
table_name
: any_name
;
column_name
: any_name
;
any_name
: IDENTIFIER
| keyword
// | '(' any_name ')'
;
keyword
: K_AND
| K_NOT
| K_NULL
| K_IN
| K_OR
;
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
: '\"' ( ~'\"' | '\"\"' )* '\"'
;
SPACES
: [ \u000B\t\r\n] -> channel(HIDDEN)
;
DOT : '.';
OPEN_PAR : '(';
CLOSE_PAR : ')';
COMMA : ',';
STAR : '*';
PLUS : '+';
MINUS : '-';
TILDE : '~';
DIV : '/';
MOD : '%';
AMP : '&';
PIPE : '|';
LT : '<';
LT_EQ : '<=';
GT : '>';
GT_EQ : '>=';
EQ : '=';
NOT_EQ2 : '<>';
K_AND : A N D;
K_NOT : N O T;
K_NULL : N U L L;
K_OR : O R;
K_IN : I N;
fragment DIGIT : [0-9];
fragment A : [aA];
fragment B : [bB];
fragment C : [cC];
fragment D : [dD];
fragment E : [eE];
fragment F : [fF];
fragment G : [gG];
fragment H : [hH];
fragment I : [iI];
fragment J : [jJ];
fragment K : [kK];
fragment L : [lL];
fragment M : [mM];
fragment N : [nN];
fragment O : [oO];
fragment P : [pP];
fragment Q : [qQ];
fragment R : [rR];
fragment S : [sS];
fragment T : [tT];
fragment U : [uU];
fragment V : [vV];
fragment W : [wW];
fragment X : [xX];
fragment Y : [yY];
fragment Z : [zZ];
writing
| expr K_AND expr
with the input
field1=1 and field2 = 2
results in
line 1:8 mismatched input 'and' expecting {<EOF>, '||', '*', '+', '-', '/', '%', '<', '<=', '>', '>=', '=', '<>', K_AND, K_NOT, K_OR, K_IN}
while
| expr 'and' expr
works like a charm:
$ antlr4 wtfql.g4 && javac -classpath /usr/local/Cellar/antlr/4.4/antlr-4.4-complete.jar wtfql*.java && cat test.txt | grun wtfql start -tree -gui
(start (expr (expr (expr (column_name (any_name feld1))) = (expr (literal_value 1))) and (expr (expr (column_name (any_name feld2))) = (expr (literal_value 2)))) <EOF>)
What am I missing?

Answer 1

I presume "and" is an IDENTIFIER since the rule for IDENTIFIER comes before the rule for AND and thus wins.
If you write 'and' in the parser rule this implicitly creates a token (not AND!) which comes before IDENTIFIER and thus wins.
Rule of thumb: More specific lexer rules first. Don't create new lexer tokens implicitly in parser rules.
If you check the token type, you'll get a clue what's going on.