rustdoc won't show impls with enough trait indirection

[Manishearth]

pub trait IsA<T> {}

impl<T> IsA<T> for T {}

pub struct Foo;

pub trait Bar {}
impl<T: IsA<Foo>> Bar for T {}

Foo implements Bar, but this won't show up in rustdoc.

the gstreamer bindings exhibit this: https://sdroege.github.io/rustdoc/gstreamer/gstreamer/struct.DeviceMonitor.html , https://sdroege.github.io/rustdoc/gstreamer/gstreamer/trait.DeviceMonitorExt.html

This may be architecturally hard to do, in that case it may be worth looking into a doc(proxy=foo) attribute that lets you ask for an impl to explicitly show up on the page of a certain type. This also is useful in cases like #55408 where your impl is on Wrapper<Foo> but you want it to be discoverable from Foo

[Manishearth]

cc @QuietMisdreavus @GuillaumeGomez

[ollie27]

Since 1.30 rustdoc displays blanket impls on applicable types:

[Manishearth]

Huh, looks like rustdoc didn't rebuild locally