[Bug fortran/66993] New: Spurious ambiguous symbol error with submodules

[mikael at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66993

            Bug ID: 66993
           Summary: Spurious ambiguous symbol error with submodules
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mikael at gcc dot gnu.org
  Target Milestone: ---

Submodules host-associate the (sub-)module they derive from.
This means that when a symbol is use-associated with the same name as one of
the module's symbols, there is no ambiguity: the use-associated symbol has the
priority.
This doesn't work currently, as host-association as been implemented by reusing
the use-association mechanism.  Module symbols are put at the same level as
use-associated symbols, and the compiler complains about an ambiguous symbol:

test.f90:15:16:

       print *, i
                1
Error: Name ‘i’ at (1) is an ambiguous reference to ‘i’ from module ‘m’


Testcase:

module m
  integer, parameter :: i = -1
  interface
    module subroutine show_i
    end subroutine show_i
  end interface
end module m

module n
  integer, parameter :: i = 2
end module n

submodule (m) sm
  use n
contains
  module subroutine show_i
    print *, i
  end subroutine show_i
end submodule sm

program p
  use m
  call show_i
end p


I believe this should be accepted and it should print 2.