Function owned_elems_iter 

pub(crate) fn owned_elems_iter(
    access: &TokenStream,
    borrowed: bool,
    elem_ty: &Type,
) -> TokenStream

The elements of an expanded Vec<T> / Box<[T]> / &[T] field value access as an iterator of owned T: moved out of an owned container, cloned out of a borrowed slice. IntoIterator::into_iter is called by path so a Box<[T]> iterates by value in every edition.