Polymorphic array in a derived type

[St_Maxwell]

@FortranFan

  type :: t
      class(t), allocatable :: a
   end type
end 

Yes, this piece of code does not compile in gfortran.

@FortranFan

module m

   type, abstract :: root_t
   end type

   type :: base_wrapper !<-- or even type, extends(root_t) :: base_wrapper
     class(root_t), allocatable :: val
   end type

   type, extends(root_t) :: base
     character(len=10) :: name
     type(base_wrapper), allocatable :: list(:)
   end type

   type, extends(base) :: child
   end type

end module

   use m

   type(child) :: obj
   obj%name = "child"

end

And this works in gfortran.

I have just read the code of an XML library (xml-fortran/tree_struct.f90 in paulromano/xml-fortran). It uses pointer instead of allocatable attribute. So I tried a pointer implementation for the code I posted, and it compiles in gfortran. I think it might be a feasible way too, although I am less willing to use pointer in general.