[Bug fortran/82275] New: gfortran rejects valid & accepts invalid reference to dimension-remapped type selector

[damian at sourceryinstitute dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82275

            Bug ID: 82275
           Summary: gfortran rejects valid & accepts invalid reference to
                    dimension-remapped type selector
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: damian at sourceryinstitute dot org
  Target Milestone: ---

$ cat reproducer.f90 
!! Associating a name with a reduced-dimension section of a
!! multidimensional array precludes subsequent use of the name
!! with the appropriately reduced dimensionality and instead
!! requires use of the (invalid) full set of original dimensions.
!! It seems that this only occurs in the presence of type guarding:
  type component
  end type
  type container
    class(component), allocatable :: component_array(:,:)
  end type
  type(container) bag
  type(component) section_copy
  allocate(component::bag%component_array(1,1))
  select type(associate_name=>bag%component_array(1,:))
    type is (component)
      section_copy = associate_name(1)  ! gfortran 5,6,7,8 reject valid
      section_copy = associate_name(1,1)! gfortran 5,6,7,8 accept invalid
  end select
end

$ gfortran reproducer.f90 
reproducer.f90:16:35:

       section_copy = associate_name(1)  ! gfortran 5,6,7,8 reject valid
                                   1
Error: Rank mismatch in array reference at (1) (1/2)
rouson@Sourcery-Linux-VM:~/Desktop/Builds/adhoc/src/gnu/nrc/rank-mismatch$
gfortran --version
GNU Fortran (GCC) 8.0.0 20170912 (experimental)