tree 9a11fab56a17cb152d54aeda40332d5e54191434
parent 3e3e06dfdd2a5c601ae69be7558c1a9fbf4f32d8
parent 4333b869729bd00b8703721e206249b237a25e72
author bors <bors@rust-lang.org> 1568610979 +0000
committer bors <bors@rust-lang.org> 1568610979 +0000

Auto merge of #64383 - pcpthm:btreeset-size-hint, r=dtolnay

Improve BTreeSet::Intersection::size_hint

A comment on `IntersectionInner` mentions `small_iter` should be smaller than `other_iter` but this condition is broken while iterating because those two iterators can be consumed at a different rate. I added a test to demonstrate this situation.
<del>I made `small_iter.len() < other_iter.len()` always true by swapping two iterators when that condition became false. This change affects the return value of `size_hint`. The previous result was also correct but this new version always returns smaller upper bound than the previous version.</del>
I changed `size_hint` to taking minimum of both lengths of iterators and renamed fields to `a` and `b` to match `Union` iterator.