--- /dev/null
+! { dg-do compile }
+! PR fortran/96556 - this used to cause an ICE.
+! Test case by Juergen Reuter.
+module polarizations
+
+ implicit none
+ private
+
+ type :: smatrix_t
+ private
+ integer :: dim = 0
+ integer :: n_entry = 0
+ integer, dimension(:,:), allocatable :: index
+ contains
+ procedure :: write => smatrix_write
+ end type smatrix_t
+
+ type, extends (smatrix_t) :: pmatrix_t
+ private
+ contains
+ procedure :: write => pmatrix_write
+ procedure :: normalize => pmatrix_normalize
+ end type pmatrix_t
+
+contains
+
+ subroutine msg_error (string)
+ character(len=*), intent(in), optional :: string
+ end subroutine msg_error
+
+ subroutine smatrix_write (object)
+ class(smatrix_t), intent(in) :: object
+ end subroutine smatrix_write
+
+ subroutine pmatrix_write (object)
+ class(pmatrix_t), intent(in) :: object
+ call object%smatrix_t%write ()
+ end subroutine pmatrix_write
+
+ subroutine pmatrix_normalize (pmatrix)
+ class(pmatrix_t), intent(inout) :: pmatrix
+ integer :: i, hmax
+ logical :: fermion, ok
+ do i = 1, pmatrix%n_entry
+ associate (index => pmatrix%index(:,i))
+ if (index(1) == index(2)) then
+ call error ("diagonal must be real")
+ end if
+ end associate
+ end do
+ contains
+ subroutine error (msg)
+ character(*), intent(in) :: msg
+ call pmatrix%write ()
+ end subroutine error
+ end subroutine pmatrix_normalize
+
+end module polarizations