The following code generate internal g++ compiler fault during compilation:
file y.cc:

class A {
  class B {
  };
};

void
A::B::f() {
}

with the following diagnostics:

y.cc:7: no `void A::B::f ()' member function declared in class `A::B'
y.cc:7: Internal error: Segmentation fault.
Please submit a full bug report.
See <URL:http://bugzilla.redhat.com/bugzilla/> for instructions.

Regards,
Nikolaj Logvinov