[Bug c++/101099] New: [9/10/11/12 Regression] ICE in type_unification_real, at cp/pt.c:22173

["gscfq@t-online.de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101099

            Bug ID: 101099
           Summary: [9/10/11/12 Regression] ICE in type_unification_real,
                    at cp/pt.c:22173
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gscfq@t-online.de
  Target Milestone: ---

Started with r9 between and 20190615 and 20190727, r8 accepts it.
With options -std=gnu++11 -fconcepts and several testsuite files
or the following variant :


$ cat z1.cc
#include <initializer_list>
constexpr auto list = { 1, 2, 3 };


$ g++-8 -c z1.cc -std=gnu++11 -fconcepts
$
$ g++-12-20210613 -c z1.cc -std=gnu++11 -fconcepts
z1.cc:2:33: internal compiler error: in type_unification_real, at cp/pt.c:22173
    2 | constexpr auto list = { 1, 2, 3 };
      |                                 ^
0x8313d8 type_unification_real
        ../../gcc/cp/pt.c:22173
0x819606 do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int)
        ../../gcc/cp/pt.c:29619
0x745bf6 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
        ../../gcc/cp/decl.c:7834
0x802791 cp_parser_init_declarator
        ../../gcc/cp/parser.c:22044
0x7e348a cp_parser_simple_declaration
        ../../gcc/cp/parser.c:14587
0x8081f5 cp_parser_declaration
        ../../gcc/cp/parser.c:14284
0x80770b cp_parser_translation_unit
        ../../gcc/cp/parser.c:4942
0x80770b c_parse_file()
        ../../gcc/cp/parser.c:45611
0x8d7412 c_common_parse_file()
        ../../gcc/c-family/c-opts.c:1219