[Bug fortran/106731] New: ICE on automatic array of derived type with DTIO

[federico.perini at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106731

            Bug ID: 106731
           Summary: ICE on automatic array of derived type with DTIO
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: federico.perini at gmail dot com
  Target Milestone: ---

A derived type that has user-defined I/O causes ICE on all gfortran versions 7
to 12.1.0, whenever it's being used as an automatic object.

The error is at 


   63 |         type(t) :: automatic(n)
      |                               1
internal compiler error: in gfc_trans_auto_array_allocation, at
fortran/trans-array.cc:6617

This does not happen if the derived type is allocated.

Here's the simplest example: 

module causes_ice
    implicit none

    type :: t
        real(8) :: x
        contains
        procedure, private :: write_formatted
        generic :: write(formatted) => write_formatted
    end type t

    contains

    subroutine write_formatted(this, unit, iotype, v_list, iostat, iomsg)
       class(t), intent(in) :: this
       integer, intent(in) :: unit
       character(*), intent(in) :: iotype
       integer, intent(in) :: v_list(:)
       integer, intent(out) :: iostat
       character(*), intent(inout) :: iomsg
       write(unit, '(a)', iostat=iostat, iomsg=iomsg) 'dummy'
    end subroutine write_formatted

end module causes_ice

module use_t
    use causes_ice
    implicit none

    public :: automatic_alloc

    contains

    subroutine automatic_alloc(n)
        integer, intent(in) :: n

        ! Automatic array: ICE!
        type(t) :: automatic(n)

        ! Allocatable: works
        type(t), allocatable :: alloc(:)
        allocate(alloc(n))

        ! Do anything
        print *, 'n=',n,automatic(n)%x

    end subroutine automatic_alloc

end module use_t

program test
    use use_t
    call automatic_alloc(1)
end program test

I could find other DTIO-related bugs, but none seemed related with the
allocation type.