Ambiguity in Conversion Operators

EDG based compilers (Intel, Comeau) fail on the following code

struct A;
//typedef int A;

struct B {
  operator const A & ();
};

void g(const A &);
void g(A &);

int main() {
  g(B());
}

(separate file)

with the error

error: more than one instance of overloaded function "g"
          matches the argument list, the choices that match are:
            function "g(const A &)"
            function "g(A &)"
            The argument types that you used are: (B)
    g(B());

but do not fail when the typedef is used in place of the struct.

I have reported this to EDG and Comeau, with no replies. I would report it to Intel, but they have made doing so quite difficult by designing their website poorly.

Update: EDG replied, saying it was a bug. [an error occurred while processing this directive]