To: J3                                                     J3/22-108
From: John Reid
Subject: Allocating unlimited-polymorphic objects
Date: 2022-January-15
References: 22-007, 21-199r1, 22-104

Discussion
----------

If a non-coarray <allocate-object> of unlimited-polymorphic type were
allowed to be allocated to have a dynamic type with a coarray potential
subobject component, its deallocation would be an image control
statement. It was intended to disallow this because it is undesirable
to have a data value determine whether a statement is an image control
statement.

The dynamic type given to an <allocate-object> of unlimited-polymorphic
type is the type specified by <type-spec> or the dynamic type of
<source-expr>. 21-199r1 proposed adding
"If an <allocate-object> is unlimited polymorphic, the dynamic
type of neither <type-spec> nor <source-expr> shall have a
coarray potential subobject component."
The editor changed this (see 22-104) to
"If an <allocate-object> is unlimited polymorphic, the dynamic
type of <source-expr> shall not have a coarray potential subobject
component."
because the suggested restriction on <type-spec> can be expressed as a
constraint.

The editor made this new edit
[142:5-6] C941,
    "or type TEAM_TYPE" -> "type TEAM_TYPE",
    after "ISO_FORTRAN_ENV" insert
        ", or a type that has a coarray potential subobject component".
Unfortunately, this constraint starts
"If an allocate-object is a coarray,"
rather than
"If an <allocate-object> is unlimited polymorphic,"
so a new constraint is needed.

The restriction on <source-expr> can also be expressed as a constraint.
A restriction on its declared type is sufficient in view of the
constraint on <derived-type-def>:
C741 (R726) If EXTENDS appears and the type being defined has a coarray
     potential subobject component, its parent type shall have a coarray
     potential subobject component.

A new constraint on the type specified by <type-spec> and the declared
type of <source-expr> is proposed. This replaces the two changes made
to 21-007r2 that were discussed above.


Edits to 22-007
--------------

[142:5-6] In 9.7.1.1 Form of the ALLOCATE statement, C941, change
"type TEAM_TYPE" to  "or type TEAM_TYPE" and delete
", or a type that has a coarray potential subobject component"
so that it reads
"C941 (R929) If an allocate-object is a coarray, type-spec shall not
specify type C_PTR or C_FUNPTR from the intrinsic module ISO_C_BINDING,
or type TEAM_TYPE from the intrinsic module ISO_FORTRAN_ENV."

[142:6+] In 9.7.1.1 Form of the ALLOCATE statement, after
"C941 (R929) If an allocate-object is a coarray, ..." add
"C941a (R929) If an <allocate-object> is unlimited polymorphic, neither
the type specified by <type-spec> nor the declared type of <source-expr>
shall have a coarray potential subobject component."

[143:11-12] In 9.7.1.1 Form of the ALLOCATE statement, para 5, delete
the final sentence
"If an <allocate-object> is unlimited polymorphic, the dynamic type of
<source-expr> shall not have a coarray potential subobject component."