https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127541
Bug ID: 127541
Summary: The type of array constructors can be polymorphic
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: mikael at gcc dot gnu.org
Target Milestone: ---
Consider this testcase:
program prog
implicit none
type :: t1
integer :: c1
end type
type, extends(t1) :: t2
integer :: c2
end type
class(t1), allocatable :: x(:), y(:), z(:)
x = [t2(2, 3), t2(5, 7)]
y = [t2(11, 13), t2(17, 19)]
print *, [x, y]
z = [x, y]
print *, storage_size(z)
select type (z)
type is (t1)
print *, "OK"
class default
print *, "FAIL"
end select
end program
This is rejected with:
12 | print *, [x, y]
| 1
Error: Data transfer element at (1) cannot be polymorphic unless it is
processed by a defined input/output procedure
It is questionable that the type of the array constructor is polymorphic.
F2023 (7.8 Construction of array values):
> If type-spec is omitted, corresponding length type parameters of the declared
> type of each ac-value expression shall have the same value; in this case, the
> declared type and type parameters of the array constructor are those of the
> ac-value expressions.
and one paragraph later:
> The dynamic type of an array constructor is the same as its declared type.
According to this, the type (both declared and dynamic type) of the array
constructor above is t1, despite x and y both having dynamic type of t2.
My question is: is it type(t1) or class(t1) with a dynamic type of t1?
In the former case the error is bogus; in the latter case it is not.
I tend to think the type is type(t1), so non-polymorphic, as the dynamic type
is not allowed to be different from the declared type.
