[Bug fortran/81447] New: gfortran fails to recognize the exact dynamic type of a polymorphic entity that was allocated in a external procedure

["mathewc at nag dot co.uk" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81447

            Bug ID: 81447
           Summary: gfortran fails to recognize the exact dynamic type of
                    a polymorphic entity that was allocated in a external
                    procedure
           Product: gcc
           Version: 7.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mathewc at nag dot co.uk
  Target Milestone: ---

> uname -a && gfortran --version && cat foo.f90 && gfortran foo.f90 && ./a.out
Linux cuivienen.nag.co.uk 4.11.9-300.fc26.x86_64 #1 SMP Wed Jul 5 16:21:56 UTC
2017 x86_64 x86_64 x86_64 GNU/Linux
GNU Fortran (GCC) 7.1.1 20170622 (Red Hat 7.1.1-3)
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Module m
  Type :: t
  End Type
End Module
Program p
  Use m
  Class (t), Allocatable :: x
  Interface
    Subroutine s(x)
      Use m
      Class (t), Allocatable :: x
    End Subroutine
  End Interface
  Call s(x)
  Select Type (x)
  Type Is (t)
    Continue
  Class Is (t)
    Stop 'Inconceivable t'
  Class Default
    Stop 'Inconceivable *'
  End Select
  Print *, 'ok'
End Program
Subroutine s(x)
  Use m, Only: t
  Implicit None
  Class (t), Allocatable :: x
  Allocate (t :: x)
End Subroutine
STOP Inconceivable t

Note that the version with s internal to p is OK:

Module m
  Type :: t
  End Type
End Module
Program p
  Use m
  Class (t), Allocatable :: x
  Call s(x)
  Select Type (x)
  Type Is (t)
    Continue
  Class Is (t)
    Stop 'Inconceivable t'
  Class Default
    Stop 'Inconceivable *'
  End Select
  Print *, 'ok'
Contains
  Subroutine s(x)
    Use m, Only: t
    Implicit None
    Class (t), Allocatable :: x
    Allocate (t :: x)
  End Subroutine
End Program
 ok