[antlr-interest] "no viable alternative at character" error for '; ' and ',' in a wild cast

[Reynold Xin]

I have the attached rules defined in ANTLR 3. I ran it (Java program)
on a simple SQL query:

SELECT abcd, wewasdf
FROM visit AS v, trial AS t
WHERE v.id = 1234 AND t.city = 'NEW YORK' AND
LINK v.diagnosis WITH t.condition USING synonym

It reports the following error:

line 1:11 no viable alternative at character ','
line 2:15 no viable alternative at character ','
line 3:11 no viable alternative at character '='
line 3:29 no viable alternative at character '='

Those characters should be accepted in rule select_until_link_or_semi,
which is defined as (~(LINK | ';'))* .

If I add ',' and '=' to the grammar definition of LETTER, the error is
gone. However, that changes the behaviour of LETTER. How can I fix
this problem?

Thanks.

-----------------------------------------
Rules
-----------------------------------------

select_stmt
       :       SELECT clause=select_until_link_or_semi
link_clause_expr opt_semicol
       {
              ...
       }
       ;

select_until_link_or_semi
    :    (~(LINK | ';'))*
    ;

NATIVE_LINK
       :       'SYNONYM' | 'HYPONYM' | 'WEIGHTEDJACCARD' ;

WORD    :       LETTER (LETTER|DIGIT|'.')* ;

NUMBER  :       DIGIT+ ;

WHITESPACE
       :       ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ;

// hexadecimal digit
fragment HEX_DIGIT
       :       ('0'..'9'|'A'..'F'|'a'..'f')
       ;

// digit
fragment DIGIT
       :       '0'..'9';

// letters
fragment LETTER
       :       'a'..'z' | 'A'..'Z' | '_' | '$' | '#';

--
Reynold Xin