Lvalue awareness in ANTLR grammar and syntax predicates - antlr

Question

I am implementing a parser with ANTLR for D. This language is based on C so there are some ambiguity around the declarations and the expressions. Consider this:
a* b = c; // This is a declaration of the variable d with a pointer-to-a type.
c = a * b; // as an expression is a multiplication.
As the second example could only appear on the right of an assignment expression I tried to resolve this problem with the following snippet:
expression
: left = assignOrConditional
(',' right = assignOrConditional)*
;
assignOrConditional
: ( postfixExpression ('=' | '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '~=' | '<<=' | '>>=' | '>>>=' | '^^=') )=> assignExpression
| conditionalExpression
;
assignExpression
: left = postfixExpression
( op = ('=' | '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '~=' | '<<=' | '>>=' | '>>>=' | '^^=')
right = assignOrExpression
)?
;
conditionalExpression
: left = logicalOrExpression
('?' e1 = conditionalExpression ':' e2 = conditionalExpression)?
;
As far as my understanding goes, this should do the trick to avoid the ambiguity but the tests are failing. If I feed the interpreter with any input, starting with the rule assignOrConditional, it will fail with NoViableAltException.
the inputs were
a = b
b-=c
d
Maybe I'm misunderstanding how the predicates are working therefore it would be great if someone could correct my explanation to the code: If the input can be read as a postfixExpression it will check if the next token after the postfixExpression is one of the assignment operators and if it is, it will parse the rule as an assignmentExpression. (Note, that the assignmentExpression and the conditionalExpression works well). If the next token isn't of them, it tries to parse it as a conditionalExpression.
EDIT
[solved] Now, there's an other problem with this solution that I could realize: the assignmentExpression has to choose in it's right hand expression is an assignment again (that is, postfix and assignment operator follows), if it is chained up.
Any idea what's wrong with my understanding?

Answer 1

If I feed the interpreter with any input, ...
Don't use ANTLRWorks' interpreter: it is buggy, and disregards any type of predicate. Use its debugger: it works flawlessly.
If the input can be read as a postfixExpression it will check if the next token after the postfixExpression is one of the assignment operators and if it is, it will parse the rule as an assignmentExpression.
You are correct.
EDIT [solved] Now, there's an other problem with this solution that I could realize: the assignmentExpression has to choose in it's right hand expression is an assignment again (that is, postfix and assignment operator follows), if it is chained up.
What's wrong with that?