[Bug c++/98885] [modules] forward declaration of classes prevent them from being exported at the point of actual declaration

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98885

--- Comment #7 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
My mistake.  interface and implementation partitions do not follow the
non-partition behaviour.  You have two M:A partitions (one an interface and one
an implementation).  This is what you want:

A.cc:
export module M:A;
export class B;
export
class A
{
  void
  f(B const &) const;
};


B.cc:
export module M:B;
export class A;
export
class B
{
  void
  f(A const &) const;
};

M.cc:
export module M;

export import :A;
export import :B;

M-impl.cc:
module M;

void
A::f(B const &) const {}
void
B::f(A const &) const {}


devvm1702:10>./cc1plus -fmodules-ts -quiet A.cc     
devvm1702:11>./cc1plus -fmodules-ts -quiet B.cc     
devvm1702:12>./cc1plus -fmodules-ts -quiet M.cc     
devvm1702:13>./cc1plus -fmodules-ts -quiet M-impl.cc


you could of course split M-impl.cc into two if you want, one for the A bits
and one for the B bits