Generics confusion in docs

[mvdnes]

Description

Recently I was looking in the docs for FilterMap, where it says:

fn filter_map<B>(|B|: 'r -> Option<B>) -> FilterMap<'r, B, B, FilterMap<'a, A, B, T>>

However, it seems that not all B's must be the same type. The definition of filter_map is namely:

fn filter_map<'r, B>(self, f: |A|: 'r -> Option<B>) -> FilterMap<'r, A, B, Self>

I believe this is due to the fact that the function filter_map is implemented for Iterator<A> and that FilterMap implements Iterator<B>.

[bluss]

Compare with core docs: http://doc.rust-lang.org/core/iter/struct.FilterMap.html

This is issue #15099

[steveklabnik]

Since #15099 is fixed, I'm closing this. Please let me know if something is changed!

[bluss]

It looks like it might be a separate issue -- the reported bug still exists, and core and std docs are still not equal for the trait implementations section.

[steveklabnik]

Apparently so.

[steveklabnik]

These signatures have changed entirely, I'm not sure if they're still wrong, but they are slightly different...

[mvdnes]

Confusion in some form arises in the following code

pub trait MyImpl<A> {
    fn myimpl_fun<B>(&self, _: A) -> Option<B> {
        None
    }   
}

pub struct MyStruct<B> {
    _data: B,
}

impl<B> MyImpl<B> for MyStruct<B> {}

Running the doc, we get

impl<B> MyImpl<B> for MyStruct<B>
    fn myimpl_fun<B>(&self, _: A) -> Option<B>

In this case, the A should actually be a B, and the B's from the function something else.

[alexcrichton]

I believe this is a dupe of #14072, so closing in favor of that.