[Bug c++/114917] New: [modules] Explicit specialisations in export namespace not permitted

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114917

            Bug ID: 114917
           Summary: [modules] Explicit specialisations in export namespace
                    not permitted
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nshead at gcc dot gnu.org
  Target Milestone: ---

Since r15-84-g79420dd3441458 we now incorrectly reject the following modules
example:

  export module M;
  export namespace ns {
    template <typename T> void foo() {}
    template <> void foo<int>() {}
  }

Relatedly, we also incorrectly accept (and have since at least GCC 4.1):

  extern "C++" namespace ns {
    struct Incomplete;
    Incomplete bar;
  }

for similar reasons: the contents of the namespace are still considered be an
"unbraced" context of the extern "C++" and so bar is implicitly considered to
be declared extern.  See also [dcl.link] p8.