[Bug c++/103701] New: C++20 modules create internal compiler error at import_export_decl

["lightningdzeyenr at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103701

            Bug ID: 103701
           Summary: C++20 modules create internal compiler error at
                    import_export_decl
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lightningdzeyenr at gmail dot com
  Target Milestone: ---

When trying to compile a C++ file which uses modules from C++20, I get the
following output:

In module imported at hajime.cpp:24:9:
Hajime:Installer: note: unable to represent further imported source locations
hajime.cpp:182:1: internal compiler error: in import_export_decl, at
cp/decl2.c:3060
  182 | }
      | ^
0xe30681 internal_error(char const*, ...)
        ???:0
0xe27235 fancy_abort(char const*, int, char const*)
        ???:0
0xf9fe77 c_parse_final_cleanups()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-11/README.Bugs> for instructions.

For the GCC version, I'm using 11.1.0 (Ubuntu 11.1.0-1ubuntu1~21.04) on a
x86_64 system. The compile command that produced the exact above output is
this:

g++-11 -std=c++20 -fmodules-ts hajime.cpp

For the rest of the GCC configuration, here it is:

Using built-in specs.
COLLECT_GCC=g++-11
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
11.1.0-1ubuntu1~21.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-11
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-11-RPS7jb/gcc-11-11.1.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-RPS7jb/gcc-11-11.1.0/debian/tmp-gcn/usr
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd

Finally, I've included the .ii file that was made with -save-temps. Just in
case you want to see the original code that causes this error, this GitHub repo
has it all: https://github.com/Slackadays/Hajime/tree/modules/source