[Bug c++/80241] New: [5/6/7 Regression] Broken error message + ICE with invalid attribute

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80241

            Bug ID: 80241
           Summary: [5/6/7 Regression] Broken error message  + ICE with
                    invalid attribute
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: diagnostic, ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
  Target Milestone: ---

The following invalid code snippet triggers a broken error message
followed by an ICE since GCC 5.2.0:

=================================================
template <typename... T> struct A
{
  [[gnu::aligned (alignof(A))...]] char c;
};

A<int> a;
=================================================

bug.cc:3:30: error: expansion pattern '#'tree_list' not supported by
dump_expr#<expression error>' contains no argument packs
   [[gnu::aligned (alignof(A))...]] char c;
                              ^~~
bug.cc:3:41: internal compiler error: tree check: expected tree_list, have
error_mark in is_late_template_attribute, at cp/decl2.c:1119
   [[gnu::aligned (alignof(A))...]] char c;
                                         ^
0x100872c tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ../../gcc/gcc/tree.c:9817
0x6e946d tree_check(tree_node*, char const*, int, char const*, tree_code)
        ../../gcc/gcc/tree.h:3064
0x6e946d is_late_template_attribute
        ../../gcc/gcc/cp/decl2.c:1119
0x6e946d splice_template_attributes
        ../../gcc/gcc/cp/decl2.c:1179
0x6e946d save_template_attributes
        ../../gcc/gcc/cp/decl2.c:1205
0x6e946d cplus_decl_attributes(tree_node**, tree_node*, int)
        ../../gcc/gcc/cp/decl2.c:1420
0x6f036d grokfield(cp_declarator const*, cp_decl_specifier_seq*, tree_node*,
bool, tree_node*, tree_node*)
        ../../gcc/gcc/cp/decl2.c:951
0x71da83 cp_parser_member_declaration
        ../../gcc/gcc/cp/parser.c:23392
0x71e63a cp_parser_member_specification_opt
        ../../gcc/gcc/cp/parser.c:22941
0x71e63a cp_parser_class_specifier_1
        ../../gcc/gcc/cp/parser.c:22094
0x720bf1 cp_parser_class_specifier
        ../../gcc/gcc/cp/parser.c:22346
0x720bf1 cp_parser_type_specifier
        ../../gcc/gcc/cp/parser.c:16419
0x721ada cp_parser_decl_specifier_seq
        ../../gcc/gcc/cp/parser.c:13326
0x71d275 cp_parser_single_declaration
        ../../gcc/gcc/cp/parser.c:26621
0x73f19c cp_parser_template_declaration_after_parameters
        ../../gcc/gcc/cp/parser.c:26315
0x73ee2c cp_parser_explicit_template_declaration
        ../../gcc/gcc/cp/parser.c:26550
0x73ee2c cp_parser_template_declaration_after_export
        ../../gcc/gcc/cp/parser.c:26569
0x746fa9 cp_parser_declaration
        ../../gcc/gcc/cp/parser.c:12445
0x748abb cp_parser_declaration_seq_opt
        ../../gcc/gcc/cp/parser.c:12372
0x748d9a cp_parser_translation_unit
        ../../gcc/gcc/cp/parser.c:4366
Please submit a full bug report, [etc.]