The following code will crash clang trunk (r117648):

template <int i> class A {
  class B* g;
};
class B {
  void f () {}
};
template class A<0>;


Output:
clang: /home/steffen/prog/llvm/tools/clang/lib/Sema/../../include/clang/AST/DependentDiagnostic.h:178: clang::DeclContext::ddiag_iterator clang::DeclContext::ddiag_begin() const: Assertion `isDependentContext() && "cannot iterate dependent diagnostics of non-dependent context"' failed.

Adding "class B;" at the start of the source file will fix the problem.