rustfmt-nightly 1.4.21

// rustfmt-match_block_trailing_comma: true
// rustfmt-trailing_comma: Always

fn main() {
    match foo {
        x => {},
        y => {
            foo();
        },
        _ => x,
    }
}

fn f<S, T,>(x: T, y: S,) -> T
where
    T: P,
    S: Q,
{
    x
}

impl Trait for T
where
    T: P,
{
    fn f(x: T,) -> T
    where
        T: Q + R,
    {
        x
    }
}

struct Pair<S, T,>
where
    T: P,
    S: P + Q,
{
    a: T,
    b: S,
}

struct TupPair<S, T,>(S, T,)
where
    T: P,
    S: P + Q;

enum E<S, T,>
where
    S: P,
    T: P,
{
    A { a: T, },
}

type Double<T,>
where
    T: P,
    T: Q,
= Pair<T, T,>;

extern "C" {
    fn f<S, T,>(x: T, y: S,) -> T
    where
        T: P,
        S: Q;
}

trait Q<S, T,>
where
    T: P,
    S: R,
{
    fn f<U, V,>(self, x: T, y: S, z: U,) -> Self
    where
        U: P,
        V: P;
}