Function wide_pointer_kind 

pub(crate) fn wide_pointer_kind<'ll, 'tcx>(
    cx: &GenericCx<'ll, FullCx<'ll, 'tcx>>,
    pointee_ty: Ty<'tcx>,
) -> Option<WidePtrKind>

Determines if pointee_ty is slice-like or trait-object-like, i.e. if the second field of the wide pointer is a length or a vtable-pointer. If pointee_ty does not require a wide pointer (because it is Sized) then the function returns None.