Lifetime of returned `next` references

[tommie]

I'm interested in bplustree, because it seems to allow removal/insertion without invalidating iterators, something it seems BTreeMap cannot do without cursors, which are only in nightly.

However, I'm hitting a lifetime issue with RawExclusiveIter::next:

bplustree/src/iter.rs

Line 589 in aedade2

pub fn next(&mut self) -> Option<(&K, &V)> {

The associated type in btree_map::Iter uses the container's lifetime:

type Item = (&'a K, &'a V)

which suggests the returned references should be tagged with 't in bplustree, since the underlying data should be valid even as the iterator is dropped.

[jiangzhe]

The returned references should use container's lifetime.
RawExclusiveIter is holding lock on leaf node, which prevents concurrent modification on the key value pair. They may not be valid if RawExclusiveIter is dropped.