After Alexander's commit (r253295) I see:

$ cat ice.cpp
template <typename T> struct A
{
  enum E : T;
  void h ();
};
template <typename T> enum A<T>::E : T { e1, e2 };
template <> enum A<long long>::E : long long {};
template <typename T> struct C
{
  enum class E : T;
};
C<int>::E c3 = C<int>::E::e6;

$ g++-7 ice.cpp
ice.cpp:12:27: error: ‘e6’ is not a member of ‘C<int>::E’
 C<int>::E c3 = C<int>::E::e6;
                           ^~
$ g++-trunk ice.cpp
ice.cpp:7:47: error: qsort comparator non-negative on sorted output: 1
 template <> enum A<long long>::E : long long {};
                                               ^
ice.cpp:7:47: internal compiler error: qsort checking failed
0x5ee434 qsort_chk_error
	.././../gcc/vec.c:222
0x16207c5 qsort_chk(void*, unsigned long, unsigned long, int (*)(void const*, void const*))
	.././../gcc/vec.c:274
0x7287ef insert_late_enum_def_bindings(tree_node*, tree_node*)
	.././../gcc/cp/name-lookup.c:1727
0x6923d1 finish_enum_value_list(tree_node*)
	.././../gcc/cp/decl.c:14322
0x76058c cp_parser_enum_specifier
	.././../gcc/cp/parser.c:18222
0x76058c cp_parser_type_specifier
	.././../gcc/cp/parser.c:16644
0x76e156 cp_parser_decl_specifier_seq
	.././../gcc/cp/parser.c:13568
0x773355 cp_parser_single_declaration
	.././../gcc/cp/parser.c:26972
0x774467 cp_parser_explicit_specialization
	.././../gcc/cp/parser.c:16564
0x77a426 cp_parser_declaration
	.././../gcc/cp/parser.c:12669
0x77a6eb cp_parser_declaration_seq_opt
	.././../gcc/cp/parser.c:12599
0x77a9fa cp_parser_translation_unit
	.././../gcc/cp/parser.c:4390
0x77a9fa c_parse_file()
	.././../gcc/cp/parser.c:38907
0x8c0df6 c_common_parse_file()
	.././../gcc/c-family/c-opts.c:1113