[Bug fortran/94408] Spurious error: ‘rw_nl_grid’ must be a module procedure or an external procedure

[michalak at ucar dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94408

--- Comment #1 from michalak at ucar dot edu ---
Here is a slightly more simplified version of the test.F90 program that still
demonstrates the error with gcc 9.1.0 (below). The namelist_t type from the
previous reproducer code turns out not to be necessary and has been removed
from the example. Commenting out the indicated line causes the error to go
away.  Thanks, -John 

===

module mod_input
  type config_t
    integer :: domain_id
    contains
    procedure :: init      => rw_config
    procedure :: rw_nl_grid
  end type config_t
  interface
    module subroutine rw_config (this,iunit)
      implicit none
      class (config_t) :: this
      integer, intent(in), optional :: iunit
    end subroutine rw_config
    module subroutine rw_nl_grid ( this, iunit )
      implicit none
      class (config_t) :: this
      integer, optional, intent(in) :: iunit
    end subroutine rw_nl_grid
  end interface
  contains
    module subroutine rw_config (this,iunit)
      implicit none
      class (config_t) :: this
      integer, intent(in), optional :: iunit
      call this%rw_nl_grid     ! comment this out to make error go away
    end subroutine rw_config
    module subroutine rw_nl_grid ( this, iunit )
      implicit none
      class (config_t) :: this
      integer, optional, intent(in) :: iunit
    end subroutine rw_nl_grid
end module mod_input

module neptune_write_native
  contains
  subroutine Run
    use mod_input
    type(config_t)            :: config
  end subroutine Run
end module neptune_write_native