[Bug c++/58980] New: [4.7/4.8/4.9 Regression] ICE with invalid enum declaration

["reichelt at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58980

            Bug ID: 58980
           Summary: [4.7/4.8/4.9 Regression] ICE with invalid enum
                    declaration
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org

The following invalid code snippet triggers an ICE since GCC 4.6.0:

==============================
template<typename> struct A
{ 
  enum A::B::C {};
};
==============================

bug.cc:3:14: internal compiler error: in is_ancestor, at cp/name-lookup.c:2721
   enum A::B::C {};
              ^
0x718fff is_ancestor(tree_node*, tree_node*)
        ../../gcc/gcc/cp/name-lookup.c:2720
0x65b41e cp_parser_enum_specifier
        ../../gcc/gcc/cp/parser.c:15348
0x645d81 cp_parser_type_specifier
        ../../gcc/gcc/cp/parser.c:14176
0x65e867 cp_parser_decl_specifier_seq
        ../../gcc/gcc/cp/parser.c:11449
0x665c33 cp_parser_member_declaration
        ../../gcc/gcc/cp/parser.c:19931
0x645fdd cp_parser_member_specification_opt
        ../../gcc/gcc/cp/parser.c:19786
0x645fdd cp_parser_class_specifier_1
        ../../gcc/gcc/cp/parser.c:19030
0x645fdd cp_parser_class_specifier
        ../../gcc/gcc/cp/parser.c:19257
0x645fdd cp_parser_type_specifier
        ../../gcc/gcc/cp/parser.c:14204
0x65e867 cp_parser_decl_specifier_seq
        ../../gcc/gcc/cp/parser.c:11449
0x664443 cp_parser_single_declaration
        ../../gcc/gcc/cp/parser.c:22748
0x66494c cp_parser_template_declaration_after_export
        ../../gcc/gcc/cp/parser.c:22624
0x670969 cp_parser_declaration
        ../../gcc/gcc/cp/parser.c:10849
0x66f4f8 cp_parser_declaration_seq_opt
        ../../gcc/gcc/cp/parser.c:10771
0x670e36 cp_parser_translation_unit
        ../../gcc/gcc/cp/parser.c:4007
0x670e36 c_parse_file()
        ../../gcc/gcc/cp/parser.c:31045
0x791113 c_common_parse_file()
        ../../gcc/gcc/c-family/c-opts.c:1046
Please submit a full bug report, [etc.]