[flang] Structure constructor issue with parent component

[DanielCChen]

Consider the following code:

program main

    type A
        class(*), pointer :: u1(:)
    end type

    type, extends(A) :: B
    end type

    type(B), target :: b1
    type(A), pointer :: ptr(:)

    allocate(ptr(2))

    b1 = B(ptr)     !! FAIL
!    b1 = B(u1=ptr)  !! WORK

end program

When the u1 component is of unlimited-poly, Flang seems take ptr as the parent component in the structure constructor because it is of type A.
However, the standard seems requires component keyword for the parent component.

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` program main

type A
    class(*), pointer :: u1(:)
end type

type, extends(A) :: B
end type

type(B), target :: b1
type(A), pointer :: ptr(:)

allocate(ptr(2))

b1 = B(ptr)     !! FAIL

! b1 = B(u1=ptr) !! WORK

end program

When the `u1` component is of unlimited-poly, Flang seems take `ptr` as the parent component in the structure constructor because it is of type `A`. 
However, the standard seems requires component keyword for the parent component.

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