[Bug fortran/79447] New: [F08] gfortran rejects valid & accepts invalid internal subprogram submodule

[damian at sourceryinstitute dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79447

            Bug ID: 79447
           Summary: [F08] gfortran rejects valid & accepts invalid
                    internal subprogram submodule
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: damian at sourceryinstitute dot org
  Target Milestone: ---

A recent build of gfortran 7 doesn’t allow an internal subprogram to be
contained inside a module subprogram when the subprogram is in a submodule and
is implemented with the “module procedure” keywords instead of “module
subroutine”.  See below.  gfortran 6.3.0 exhibits the same behavior.  It would
be great if any fix can also be back-ported to the 6 branch.

ifort 17 compiles the code below without error.  

Damian


$ cat procedure-contains.f90 
module foo_interface
  implicit none
  interface
    module subroutine foo()
    end subroutine
  end interface
end module foo_interface

submodule(foo_interface) foo_implementation
contains
    module procedure foo
    contains
      module subroutine bar()
      end subroutine
    end procedure
   !end subroutine ! gfortran accepts this invalid workaround
end submodule 

$ gfortran procedure-contains.f90 
procedure-contains.f90:15:7:

     end procedure
       1
Error: Expecting END SUBROUTINE statement at (1)
procedure-contains.f90:17:3:

 end submodule
   1
Error: Expecting END SUBROUTINE statement at (1)
f951: Error: Unexpected end of file in 'procedure-contains.f90'

$ gfortran --version
GNU Fortran (MacPorts gcc7 7-20170108_0) 7.0.0 20170108 (experimental)