Rustdoc does not populate documentation from external traits

[alexcrichton]

If a type implements a trait which was defined in an external crate, then the documentation on the methods along with the default methods will not be shown in the documentation for the host crate.

I don't think that there's a large number of other issues with cross-crate documentation, so I'm not going to make this a blanket "cross-crate rustdoc needs" work issue.

Soon, cross-crate implementations of traits will not slurp in the default methods to show in the implementation documentation as well. Notable this means that TreeMap won't show up as having an insert method. This is bad.

[huonw]

@alexcrichton did #14346 fix this satisfactorily?

[alexcrichton]

Aha, it did indeed! For example HashMap now says it has an insert method.