dyn and :: should have a space between

[agrover]

When given this code:

fn foo(_x: &u64) -> Option<&(dyn ::std::error::Error + 'static)> {
    None
}

rustfmt 1.2.2 stable removes the space between dyn and ::, resulting in this:

fn foo(_x: &u64) -> Option<&(dyn::std::error::Error + 'static)> {
    None
}

[topecongiro]

We need to use edition 2018 to use the dyn syntax with a path that starts with ::. If you are using edition 2015 in your project, then you need to write like (dyn (::std::error::Error)).

cc rust-lang/rust#49218 (comment)

[agrover]

This is with edition 2018. Please reopen?

[sinkuu]

It seems that rustfmt (on playground) correctly adds spacing if edition is set to 2018. I guess https://github.com/rust-lang/rustfmt#rusts-editions fixes your problem.

[agrover]

No, we are using 2018 edition.

• git clone https://github.com/mozilla/neqo.git
• Observe that neqo-transport/Cargo.toml sets edition = "2018"
• Observe that neqo-transport/src/lib.rs line 120 is mis-formatted.

[agrover]

Oops, I can't repro with cargo fmt -- --check, this is happening with emacs rust-mode autoformat-on-save, so I think it is to blame, not rustfmt. Sorry to bother y'all.