ANTLR v3 grammar for boolean/conditional expression - grammar

Question

I'm taking a first stab at creating a grammar for expressions like:
(foo = bar or (bar = "bar" and baz = 45.43)) and test = true
My grammar so far looks like:
grammar filter;
tokens {
TRUE = 'true';
FALSE = 'false';
AND = 'and';
OR = 'or';
LT = '<';
GT = '>';
EQ = '=';
NEQ = '!=';
PATHSEP = '/';
LBRACK = '[';
RBRACK = ']';
LPAREN = '(';
RPAREN = ')';
}
expression : or_expression EOF;
or_expression : and_expression (OR or_expression)*;
and_expression : term (AND term)*;
term : atom ( operator atom)? | LPAREN expression RPAREN;
atom : ID | INT | FLOAT | STRING | TRUE | FALSE;
operator : LT | GT | EQ | NEQ;
INT : '0'..'9'+;
FLOAT : ('0'..'9')+ '.' ('0'..'9')*;
STRING : '"' ('a'..'z'|'A'..'Z'|'_'|' ')* '"';
ID : ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*;
But in ANTLRWorks 1.4.3, I get the parse tree:
But for the life of me I can't figure out what is wrong with my grammar. What token is it missing here?
Many thanks in advance.
Edit: To clarify the atom ( operator atom)? alternative in the atom production, I should perhaps mention that atoms should be able to be free-standing without comparison to another atom. E.g. a or b is a valid expression.

Answer 1

I'm answering to my own question here. I found two problems with my grammar. The first was easy to spot; I had put EOF at the end of my top-level rule:
expression : or_expression EOF;
The EOF was thus the missing token. My solution was remove the EOF from the expression rule, and instead introduce a rule above it:
filter: expression EOF;
The second problem was that my or_expression rule should be:
or_expression : and_expression (OR and_expression)*;
and not
or_expression : and_expression (OR or_expression)*;
The full corrected grammar is:
grammar filter;
tokens {
TRUE = 'true';
FALSE = 'false';
AND = 'and';
OR = 'or';
LT = '<';
GT = '>';
EQ = '=';
NEQ = '!=';
PATHSEP = '/';
LBRACK = '[';
RBRACK = ']';
LPAREN = '(';
RPAREN = ')';
}
filter: expression EOF;
expression : or_expression;
or_expression : and_expression (OR and_expression)*;
and_expression : term (AND term)*;
term : atom (operator atom)? | LPAREN expression RPAREN;
atom : ID | INT | FLOAT | STRING | TRUE | FALSE;
operator : LT | GT | EQ | NEQ;
INT : '0'..'9'+;
FLOAT : ('0'..'9')+ '.' ('0'..'9')*;
STRING : '"' ('a'..'z'|'A'..'Z'|'_'|' ')* '"';
ID : ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*;
And the resulting parse tree is: