[Bug fortran/59202] Erroneous argument aliasing with defined assignment

[federico.perini at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59202

--- Comment #4 from federico <federico.perini at gmail dot com> ---
The self-assignment issue is present even if the derived type has no
allocatable components. Here is a sample test program that gives an error with
gfortran 10.2.0: 

module assign
        implicit none
        private


        type, public :: t
             integer :: a              
             contains
                   procedure :: destroy=>t_destroy
                   procedure :: assign=>t_assign
                   generic :: assignment(=) =>assign 
        end type t

   contains


   elemental subroutine t_destroy(this)
        class(t), intent(inout) :: this
        this%a = 0
   end subroutine t_destroy

   subroutine t_assign(this,that)
        class(t), intent(inout) :: this
        class(t), intent(in) :: that

        call this%destroy() ! Clean memory first

        select type (thatPtr=>that)
           type is (t)
               this%a = thatPtr%a    
        end select

   end subroutine t_assign
end module assign

program test
        use assign
        type(t), allocatable :: t1(:)

        allocate(t1(10))

        do i=1,10
          t1(i)%a = i
        end do  

        n = 0
        do i=1,10
          if (mod(i,2)/=0) then 
              n = n + 1
              t1(n) = t1(i)
              print *, 'i=',i,' t(i)%a=',t1(i)%a,' expected t(i)%a=',i,':
',merge('ERROR!','OK    ',t1(i)%a/=i)
          endif
        end do

end program test