rustdoc: reexported type aliases are not preserved in function signatures

The recently added iterate function uses the Iterate type alias as its result type. It is correctly displayed in http://static.rust-lang.org/doc/master/core/iter/fn.iterate.html but not in http://static.rust-lang.org/doc/master/std/iter/fn.iterate.html.

Also, the lifetime 'a is dropped from the list of parameters for iterate.

[bluss]

Related to #15099

[mahkoh]

This must be fixed because it makes writing portable programs impossible.

[huonw]

@mahkoh, how does a rustdoc rendering bug affect the portability of a program?

[mahkoh]

@huonw: Type aliases are often used to hide platform specific types. If the documentation shows that a function takes a i64, but it actually takes a c_long, then it won't compile on platforms where c_long is not i64.

[icorderi]

I just run into this issue. In my case, the types being show by the doc are not even public.

You can see the problem on this doc output.
Note that Command_Algorithm should read Algorithm.
The title of the types are always correct, its the method and impl signature that show wrong.

I don't know if it helps, but the types are being aliased here in my code.

[steveklabnik]

This file:

pub use std::result::Result as Lol;

still mis-renders:

though as @icorderi mentions, the titles are correct.