Rustdoc not rendering some trait impls for BTreeSet and HashSet

[csouth3]

I noticed today that the rustdoc pages for BTreeSet and HashSet are both missing the sets' impls of BitOr, BitAnd, BitXor, and Sub. The page for (for example) BitOr itself lists HashSet and BTreeSet as implementors (http://doc.rust-lang.org/std/ops/trait.BitOr.html, though HashSet is listed twice, I don't know what's up there either), so rustdoc is aware of the implementations, but clicking through to either set's page (e.g. http://doc.rust-lang.org/std/collections/struct.HashSet.html), the trait impls aren't there.

I know for sure the impls for BTreeSet were rendered before #19448, so the fact that the impls changed from e.g. for BTreeSet<T> to for &'a BTreeSet<T> may be confusing rustdoc or something, but take that with a grain of salt, it's just a guess.

[apasel422]

This does appear to be related to the fact that the impls are for references. The IntoIterator impls for &BTreeSet and &mut BTreeSet (and the corresponding ones for the other collection types) have the same problem.