[Bug c++/80614] New: Bad mangling for noexcept abominable function types

["alisdairm at me dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80614

            Bug ID: 80614
           Summary: Bad mangling for noexcept abominable function types
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alisdairm at me dot com
  Target Milestone: ---

The following simple program complains about duplicate definitions for two
different template instantiations:

template <typename T> void fn() {}

int main() {
    fn<void() const>();
    fn<void() const noexcept>();
}


>From extensive testing (I'm validating a type traits library) it seems specific
to "abominable" function types differing only in the noexcept specification, so
is a C++17 specific failure.