[flang-commits] [flang] Get the BoxType from the RHS instead of LHS for polymorphic pointer assignment inside FORALL. (PR #164279)

[via flang-commits]

https://github.com/jeanPerier requested changes to this pull request.

Actually, I now remember why this code was using the LHS type, and this is to cover the case where the RHS is polymorphic and the LHS is not... (the opposite use case).

Here is a modified test from the issue that passes with flang-trunk but would fail after this patch:

```
module m
  TYPE :: DT
    TYPE(DT), POINTER    :: Ptr(:) => NULL()
  END TYPE

  TYPE, EXTENDS(DT) :: DT1
  END TYPE
contains

subroutine test(Tar1)
  CLASS(DT), TARGET  :: Tar1(:)
  TYPE(DT) :: T(10)
  integer :: I


  !DO I = 1, 10
  FORALL (I=1:10)            
    T(I)%Ptr => Tar1
  END FORALL
  !end do

  call test_type(T(1)%Ptr)
  DO I = 1, 10

  END DO
end subroutine

subroutine test_type(Tptr)
  class(DT) :: Tptr(:)
    SELECT TYPE (aa => Tptr)
    TYPE IS (DT1)
      print*, "in type is"
    CLASS DEFAULT
      print*, "in class default"
    END SELECT
end subroutine
end module

  use m
  TYPE(DT1), TARGET :: Tar1(10)
  call test(Tar1)

  END
```

So I think you need to BaseBoxType change the type passed to genVariableBox only when the LHS is polymorphic.

https://github.com/llvm/llvm-project/pull/164279