rust-lang/rust — pull request #19770 by csouth3 (2014-12-12 07:09:24+00:00)
Title: Use wrapper structs for iterators in `BTreeMap` and `HashMap`

This pull request converts the `Keys` and `Values` iterators of `BTreeMap` and `HashMap` from using type aliases to using wrapper structs as this is a safer solution long-term.