https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93028
--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Trying to compile test.cpp from Comment 5 again, I did see an ICE: internal compiler error: tree check: expected tree that contains ‘decl minimal’ structure, have ‘tree_list’ in lookup_type_scope_1, at cp/name-lookup.c:6492 0x1829be2 tree_contains_struct_check_failed(tree_node const*, tree_node_structure_enum, char const*, int, char const*) ../../gcc/tree.c:10071 0x83f864 contains_struct_check(tree_node*, tree_node_structure_enum, char const*, int, char const*) ../../gcc/tree.h:3311 0xa02cae lookup_type_scope_1 ../../gcc/cp/name-lookup.c:6492 0xa02fab lookup_type_scope(tree_node*, tag_scope) ../../gcc/cp/name-lookup.c:6535 0x93d757 lookup_and_check_tag ../../gcc/cp/decl.c:13990 0x93deff xref_tag_1 ../../gcc/cp/decl.c:14104 0x93e8a8 xref_tag(tag_types, tree_node*, tag_scope, bool) ../../gcc/cp/decl.c:14226 0xa34cab cp_parser_elaborated_type_specifier ../../gcc/cp/parser.c:18583 0xa328e6 cp_parser_type_specifier ../../gcc/cp/parser.c:17450 0xa2ce49 cp_parser_decl_specifier_seq ../../gcc/cp/parser.c:14120 0xa48668 cp_parser_single_declaration ../../gcc/cp/parser.c:28165 0xa477da cp_parser_template_declaration_after_parameters ../../gcc/cp/parser.c:27846 0xa484fc cp_parser_explicit_template_declaration ../../gcc/cp/parser.c:28094 0xa48556 cp_parser_template_declaration_after_export ../../gcc/cp/parser.c:28113 0xa2f573 cp_parser_template_declaration ../../gcc/cp/parser.c:15594 0xa41183 cp_parser_member_declaration ../../gcc/cp/parser.c:24332 0xa41076 cp_parser_member_specification_opt ../../gcc/cp/parser.c:24259 0xa3efdd cp_parser_class_specifier_1 ../../gcc/cp/parser.c:23400 0xa3fe34 cp_parser_class_specifier ../../gcc/cp/parser.c:23662 0xa32844 cp_parser_type_specifier ../../gcc/cp/parser.c:17424 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <https://gcc.gnu.org/bugs/> for instructions. but that got fixed by 41d93b16cac5b348b7883e259f7880b4a0addc23