[Bug fortran/41583] New: [OOP] TYPE IS rejected because of way vtable index is implemented

["burnus at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

The following program is valid but it fails to compile due to the way the
indices in vtable are implemented.

Cf. http://gcc.gnu.org/ml/fortran/2009-09/msg00298.html

========= File: bb.f90 =========
module m
type t
end type t
end module m
========= File: cc.f90 =========
module m2
  use m
  type, extends(t) :: t2
  end type t2
end module m2
========= File: dd.f90 =========
use m
use m2
type,extends(t) :: t3
end type t3

integer :: i
class(t), allocatable :: a
allocate(t3 :: a)
select type(a)
  type is(t)
    i = 1
  type is(t2)
    i = 2
  type is(t3)
    i = 3
end select
print *, i
end
========================

The error message is:

$ gfortran bb.f90 cc.f90 dd.f90
dd.f90:10.10:

  type is(t)
          1
dd.f90:12.10:

  type is(t2)
          2
Error: CASE label at (1) overlaps with CASE label at (2)


-- 
           Summary: [OOP] TYPE IS rejected because of way vtable index is
                    implemented
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41583