Rustfmt yeets const param defaults

[BoxyUwU]

Describe the bug
Rustfmt yeets const param defaults

playground

#![feature(const_generics_defaults)]
struct Foo<const N: usize = 5usize>;

fn main() {}

run cargo +nightly fmt or rustfmt or run the tool in playground etc and it gets formatted to:

#![feature(const_generics_defaults)]
struct Foo<const N: usize>;

fn main() {}

Expected behavior
it to not do this

Meta

• rustfmt version: rustfmt 1.4.37-nightly (0bd2b19 2021-04-03)
• From where did you install rustfmt?: playground/cargo
• How do you run rustfmt: playground/cargo fmt/rustfmt

[BoxyUwU]

I ended up getting distracted and looking into this a bit can probably PR a fix, no idea if its the "correct" fix

[calebcartwright]

thank you for the report and the corresponding PR! i've got a lot of issue/PR catch up to get through but will hopefully get to it shortly