[Bug fortran/92533] [F2018] Permit module names in access-stmt (public::/private::)

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92533

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Tobias Burnus from comment #4)
> Probably somewhere in module.c's gfc_use_module.

That's actually to early. gfc_use_module is run after all use statements have
been processed while the public/private statement comes much later.
Additionally for (cf. comment 1)
  use B
  use C
the information that a symbol has been loaded from B and/or C is lost – only
the true module ("A") remains. But we need to know later on that the symbol has
been loaded via B *and* C such that with "private :: B; public :: C" the
symbols are properly marked as public.
Hence, some tracking of the use-associated symbols until either resolving them
or until writing them to the .mod is needed – some kind of (symbol,
list-of-modules) container or (module, list-of-symbols)