[Bug c++/103279] New: [12 regression] ICE on llvm-compiler-rt-13: internal compiler error: canonical types differ for identical types

[slyfox at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103279

            Bug ID: 103279
           Summary: [12 regression] ICE on llvm-compiler-rt-13: internal
                    compiler error: canonical types differ for identical
                    types
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
  Target Milestone: ---

Initially observed ICE on llvm-13's compiler-rt build attempt. cvise managed to
reduce it down to:

$ cat a.c.cpp
    template <typename> struct __noexcept_move_assign_container;
    template <class _Allocator> struct basic_string {
      basic_string &operator=(basic_string &&) noexcept(
          __noexcept_move_assign_container<_Allocator>::value);
      basic_string &assign(basic_string &&) noexcept(
          __noexcept_move_assign_container<_Allocator>::value);
    };
    template <class _Allocator>
    basic_string<_Allocator> &
    basic_string<_Allocator>::operator=(basic_string &&) noexcept(
        __noexcept_move_assign_container<_Allocator>::value) {}

$ g++-12.0.0 -O3  -fPIC -fno-exceptions -std=c++20 -c a.c.cpp
a.c.cpp:11:60: internal compiler error: canonical types differ for identical
types 'basic_string<_Allocator>&
(basic_string<_Allocator>::)(basic_string<_Allocator>&&) noexcept
(__noexcept_move_assign_container<_Allocator>::value)' and
'basic_string<_Allocator>&
(basic_string<_Allocator>::)(basic_string<_Allocator>&&) noexcept
(__noexcept_move_assign_container<_Allocator>::value)'
   11 |         __noexcept_move_assign_container<_Allocator>::value) {}
      |                                                            ^
0x20cfe97 internal_error(char const*, ...)
        ???:0
0xc3166f comptypes(tree_node*, tree_node*, int)
        ???:0
0xa6b3bc duplicate_decls(tree_node*, tree_node*, bool, bool)
        ???:0
0xa778a0 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ???:0
0xa7c7c6 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ???:0
0xb834cd c_parse_file()
        ???:0
0xcb23dd c_common_parse_file()
        ???:0
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.

$ g++-12.0.0 -v
Using built-in specs.
COLLECT_GCC=/nix/store/59jdmdy3ylrpmap1bjxic1fjaq8wf96s-gcc-12.0.0/bin/g++
COLLECT_LTO_WRAPPER=/nix/store/59jdmdy3ylrpmap1bjxic1fjaq8wf96s-gcc-12.0.0/libexec/gcc/x86_64-unknown-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with:
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20211114 (experimental) (GCC)