Re: [PATCH v4 4/6] rust: rbtree: add mutable iterator

[Alice Ryhl]

On Mon, Jun 3, 2024 at 7:42 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
>
> On Mon, Jun 03, 2024 at 04:05:19PM +0000, Matt Gilbride wrote:
> [...]
> > +/// A mutable iterator over the nodes of a [`RBTree`].
> > +///
> > +/// Instances are created by calling [`RBTree::iter_mut`].
> > +pub struct IterMut<'a, K, V> {
> > +    _tree: PhantomData<&'a mut RBTree<K, V>>,
> > +    iter_raw: IterRaw<K, V>,
> > +}
> > +
> > +// SAFETY: The [`RBTreeIterator`] gives out mutable references to K and V, so it has the same
>
> s/RBTreeIterator/IterMut ?
>
> Also `IterMut` doesn't give out mutable references to K, which makes
> me think...
>
> > +// thread safety requirements as mutable references.
> > +unsafe impl<'a, K: Send, V: Send> Send for IterMut<'a, K, V> {}
> > +
>
> we can lose the constrains to `K: Sync`, right?

Either Send or Sync would be valid here, but almost all types that are
Sync are also Send, but the opposite is not the case. So I wouldn't
consider that to be loosening the constrain.

Alice