Pretty print empty blocks as {}

[dtolnay]

Example:

macro_rules! p {
    ($e:expr) => {
        println!("{}", stringify!($e));
    };
    ($i:item) => {
        println!("{}", stringify!($i));
    };
}

fn main() {
    p!(if true {});
    p!(struct S {});
}

Before:

if true { }
struct S {
}

After:

if true {}
struct S {}

This affects dbg!, as well as ecosystem uses of stringify such as in anyhow::ensure!. Printing a { } in today's heavily rustfmt'd world comes out looking jarring/sloppy.

[rust-highfive]

r? @nagisa

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[nagisa]

@bors r+

[bors]

📌 Commit b516a8c has been approved by nagisa

[bors]

⌛ Testing commit b516a8c with merge 772d51f...