Implement Clone and Debug for HashTable's Iter struct

[geeknoid]

Found those implementations missing, which is preventing me from implementing the same in encapsulating iterators.

[Amanieu]

Cloning a mutable iterator is unsound since it could be used to create multiple aliasing mutable references. All the other impls seem fine though.

[geeknoid]

Sorry, I'm still new to Rust. I understand your point and it makes sense, so I removed the implementation of Clone here. And in fact, looking at my own code, my wrapping iterators haven't been implementing this either.

However, if this leads to unsoundness, how come I was able to implement the logic in safe code and the compiler didn't complain? Should RawIter::clone be marked as unsafe so that what I did would flag a problem?

[Amanieu]

This isn't entirely safe: if you look above, the Iterator trait implementation for IterMut uses unsafe code. That unsafe code is only valid if it is the only instance of IterMut for a table.

[Amanieu]

This isn't resolved, it seem you have re-added the incorrect Clone impl.

[geeknoid]

OK, redeleted. Sorry about that.

[cuviper]

On the other hand, Debug for IterMut is fine.

[geeknoid]

To implement Debug, I needed Clone, so I just punted on IterMut alltogether.

[cuviper]

The map IterMut does it through a private iter() that only clones the inner: RawIter.

hashbrown/src/map.rs

Lines 3175 to 3183 in a69af93

	impl<K, V> fmt::Debug for IterMut<'_, K, V>
	where
	K: fmt::Debug,
	V: fmt::Debug,
	{
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_list().entries(self.iter()).finish()
	}
	}

hashbrown/src/map.rs

Lines 2137 to 2146 in a69af93

	impl<K, V> IterMut<'_, K, V> {
	/// Returns a iterator of references over the remaining items.
	#[cfg_attr(feature = "inline-more", inline)]
	pub(super) fn iter(&self) -> Iter<'_, K, V> {
	Iter {
	inner: self.inner.clone(),
	marker: PhantomData,
	}
	}
	}

[bors]

☔ The latest upstream changes (presumably #549) made this pull request unmergeable. Please resolve the merge conflicts.

[Amanieu]

@bors r+

[bors]

📌 Commit e9fd7b4 has been approved by Amanieu

It is now in the queue for this repository.

[bors]

⌛ Testing commit e9fd7b4 with merge cd9a955...

[bors]

☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing cd9a955 to master...