Since r243723 we ICE on the following testcase:
template <typename> struct A;
template <typename = A<int>> class B {};
template <class T, class U, class V> void foo (U, V) { T (0, 0); }
struct C {};
template <template <bool, bool, bool> class F, class>
void
bar ()
{
  F<0, 0, 0>::baz;
}
struct G { int l; };
template <int, int, int> struct E : C
{
  E (int, int) : e (0)
  {
    auto &m = this->m ();
    auto c = [&] { m.l; };
  }
  G &m ();
  int e;
};
struct D
{
  void
  baz () { bar<F, B<>>; }
  template <bool, bool, bool> struct F
  {
    static B<> baz () { foo<E<0, 0, 0>> (0, 0); }
  };
};

reduced from mathicgb:
src/mathicgb/ModuleMonoSet.cpp:184:1:   required from here
src/mathicgb/ModuleMonoSet.cpp:71:34: internal compiler error: in tsubst_copy, at cp/pt.c:14400
       const auto& monoid = this->monoid(); // workaround for gcc 4.5.3 issue
                            ~~~~~~^~~~~~