https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121425
Bug ID: 121425
Summary: Invalid derived type constructor using polymorphic
variable
Product: gcc
Version: 16.0
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 default DT constructor called with a variable of the correct type, but
upstream polymorphic, returns wrong data.
Fails with all versions of gfortran. I'm not sure about the standard
conformance of this, I defer to your comments... but it seems like it works
with other compilers (https://godbolt.org/z/PYcs5sGhP).
```
module types
use iso_fortran_env, only: rp => real64
type :: vec
real(rp) :: xyz(3) = 0
end type vec
type :: ax
type(vec) :: p
type(vec) :: n
end type ax
contains
subroutine use_class(v)
class(vec), intent(in) :: v ! no error if type(vec)
type(ax) :: aa
aa = ax(p=v,n=vec([1,0,0]))
if (any(nint(aa%p%xyz)/=[1,2,3])) then
print *, 'n=',aa%n%xyz
print *, 'p=',aa%p%xyz
error stop 'invalid default constructor'
endif
end subroutine use_class
end module types
program t
use types
type(vec) :: x
x = vec([1,2,3])
call use_class(x)
end program t
```
It's important in use cases where overriding the default constructor with a
function would void defining `parameter`s on the DT.
Thank you,
Federico
