Rustdoc doesn't show default type parameters

[huonw]

In

#[feature(default_type_params)];
#[crate_id="deftypar"];
#[crate_type="lib"];

/// Docs...
pub struct Foo<A = int>;

Foo gets rendered as

pub struct Foo<A>;

Docs...

but it should definitely be mentioning the = int part.

[lifthrasiir]

It should also mention that the default type parameter requires the #![feature(default_type_param)] crate attribute. Maybe we can hide the default type parameters by default and only show them at the additional action (e.g. clicking "This struct has default type parameters...").