ANTLR rule works on its own, but fails when included in another rule - antlr

Question

I am trying to write an ANTLR grammar for a reparsed and retagged kconfig file (retagged to solve a couple of ambiguities). A simplified version of the grammar is:
grammar FailureExample;
options {
language = Java;
}
#lexer::header {
package parse.failure.example;
}
reload
: configStatement*
EOF
;
configStatement
: CONFIG IDENT
configOptions
;
configOptions
: (type
| defConfigStatement
| dependsOnStatement
| helpStatement
| rangeStatement
| defaultStatement
| selectStatement
| visibleIfStatement
| prompt
)*
;
type : FAKE1;
dependsOnStatement: FAKE2;
helpStatement: FAKE3;
rangeStatement: FAKE4;
defaultStatement: FAKE5;
selectStatement:FAKE6;
visibleIfStatement:FAKE7;
prompt:FAKE8;
defConfigStatement
: defConfigType expression
;
defConfigType
: DEF_BOOL
;
//expression parsing
primative
: IDENT
| L_PAREN expression R_PAREN
;
negationExpression
: NOT* primative
;
orExpression
: negationExpression (OR negationExpression)*
;
andExpression
: orExpression (AND orExpression)*
;
unequalExpression
: andExpression (NOT_EQUAL andExpression)?
;
equalExpression
: unequalExpression (EQUAL unequalExpression)?
;
expression
: equalExpression (BECOMES equalExpression)?
;
DEF_BOOL: 'def_bool';
CONFIG : 'config';
COMMENT : '#' .* ('\n'|'\r') {$channel = HIDDEN;};
AND : '&&';
OR : '||';
NOT : '!';
L_PAREN : '(';
R_PAREN : ')';
BECOMES : '::=';
EQUAL : '=';
NOT_EQUAL : '!=';
FAKE1 : 'fake1';
FAKE2: 'fake2';
FAKE3: 'fake3';
FAKE4: 'fake4';
FAKE5: 'fake5';
FAKE6: 'fake6';
FAKE7: 'fake7';
FAKE8: 'fake8';
IDENT : (LETTER | DIGIT | '_')*;
WS : ( ' '
| '\t'
| '\r'
| '\n'
) {$channel=HIDDEN;}
;
fragment LETTER : ('a'..'z' | 'A'..'Z') ;
fragment DIGIT : '0'..'9';
With input:
config HAVE_DEBUG_RAM_SETUP
def_bool n
I can set antlrworks to parse just the second line (commenting out the first) and I get the proper defConfigStatement token emitted with the proper expression following. However, if I exercise either the configOptions rule or the configStatement rule (with the first line uncommented), my configOptions results in an empty set and a NoViableAlt exception is thrown.
What would cause this behavior? I know that the defConfigStatement rule is accurate and can parse correctly, but as soon as it's added as a potential option in another rule, it fails. I know I don't have conflicting rules, and I've made DEF_BOOL and DEF_TRISTATE rules the top in my list of lexer rules, so they have priority over the other lexer rules.
/Added since edit/
To further complicate the issue, if I move the defConfigStatement choice in the configOptions rule, it will work, but other rules will fail.
Edit: Using full, simplified grammar.
In short, why does the rule work on its own, but fail when it's in configOptions (especially since configOptions is in (A | B | C)* form)?

Answer 1

When I parse the input:
config HAVE_DEBUG_RAM_SETUP
def_bool n
with the parser generated from your grammar, I get the following parse tree:
So, I see no issues here. My guess is that you're using ANTLRWorks' interpreter: don't. It's buggy. Always test your grammar with a class of your own, or use ANTLWorks' debugger (press CTRL+D to launch is). The debugger works like a charm (without the package declaration, btw). The image I posted above is an export from the debugger.
EDIT
If the debugger doesn't work, try (temporarily) removing the package declaration (note that you're only declaring a package for the lexer, not the parser, but that might be a caused by posting a minimal grammar). You could also try changing the port number the debugger should connect to. It could be the port is already in use (see: File -> Preferences -> Debugger-tab).