To: J3                                                     J3/23-210r2
From: John Reid & Reinhold Bader & Malcolm Cohen
Subject: Interp: coarray potential subobject components
Date: 2023-October-26

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NUMBER: F23/009
TITLE: Coarray subobject of component
KEYWORDS: coarray, allocatable, array, component
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

The Introduction of Fortran 2023 says
  "A data object with a coarray component can be an array or
   allocatable."

This appears to be true for named variables, but there is a constraint
that makes it impossible for an array component or an allocatable
component:
  "C753 A data component whose type has a coarray potential subobject
        component shall be a nonpointer nonallocatable scalar and
        shall not be a coarray."

That means that given the type

    Type real_coarray
      Real,Allocatable :: c[:]
    End Type

the statements

    Type(real_coarray) x(100)
    Type(real_coarray),Allocatable :: y

are acceptable as type declaration statements, but unacceptable as
component definition statements.

Is this irregularity deliberate?

ANSWER:

No, this constraint was accidentally overlooked when extending types
with coarray components to be subobjects of arrays and allocatables.

An edit is provided to correct this mistake.

EDIT to N2218 (Fortran 2023 FDIS):

[79:constraint C753] In subclause
  Delete this constraint, which begins
    "C753 A data component whose type has a coarray"

[80:After NOTE 1] Insert new NOTE
    "NOTE 1.5
     A data component whose type has a coarray potential subobject
     component cannot be a coarray or a pointer, see constraint C825."
{C825 says "An entity whose type has a coarray potential subobject..."
 and components are certainly entities. We specifically wrote "entity"
 instead of "named variable" to cover the component case.
 I prefer to say it once and refer to it.}

SUBMITTED BY: John Reid & Reinhold Bader

HISTORY: 23-210   m231  Submitted
         23-210r1 m231  Revised
         23-210r2 m231  Passed as amended by J3 meeting 231.

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