To: J3                                                     10-209
From: R. Bader
Subject: SELECT TYPE on a coarray or coindexed object
Date: 2010 September 22
Reference: N1814

NUMBER: F08/xxxx
TITLE:  Resolving the type of a coarray or coindexed object
KEYWORDS: coarrays, polymorphism
DEFECT TYPE: Request for interpretation
STATUS: J3 consideration in progress

QUESTIONS:

Consider the following code:

module m
  type :: foo
    integer :: i = 0
  end type
end module m
program p
  use m
  class(foo), allocatable :: o_foo[:]
  integer :: j

  allocate(foo :: o_foo[*])
  if (this_image() == 1) then

    select type(a => o_foo[2])
      type is(foo)
      j = a%i
    end select

    select type(a => o_foo)
      type is(foo)
      j = a[2]%i
    end select

    select type(o_foo)
      type is(foo)
      j = o_foo[2]%i
    end select

  end if
end program p

(1) Is the first SELECT TYPE block standard-conforming?
(2) Is the second SELECT TYPE block standard-conforming?
(3) Is the third SELECT TYPE block standard-conforming?


PROPOSED ANSWERS:

(1) No.
For the ASSOCIATE construct, C803 disallows a coindexed
object to be ASSOCIATEd (to avoid references to coindexed
objects without angular brackets). The analogous
restriction for SELECT TYPE was overlooked.
(2) Yes.
This is implied by 8.1.3.3 para 1.
(3) Yes.


Addition of a NOTE is suggested to emphasize the validity
of (2) and (3).


PROPOSED EDITS:

In 8.1.9.1, para 1, add constraint

C837+ (R847) selector shall not be a coindexed object.

In 8.1.9.2, after para 8, add

NOTE 8.24+
Constraints on the use of coindexed objects ensure that a coindexed
object (on the remote image) has the same dynamic type as the
corresponding object on the local image. Thus a processor can resolve
the type or class of an associating entity on its own image and perform
definitions or references on the coindexed associating entity
inside the block selected for execution.


SUBMITTED BY: R. Bader

HISTORY: First draft August 4, 2010
         Updated with proposed edits August 5, 2010
	 Submitted September 22, 2010