[macro_use] on the same line as crate

[SuperCuber]

Currently, rustfmt will apply this change:

-#[macro_use] extern crate clap;
+#[macro_use]
+extern crate clap;

I disagree with this, #[macro_use] is closely related to the crate itself and should be on the same line.
Also, this causes a bit of confusion with examples like:

#[macro_use]
extern crate that_defines_macros;
extern crate that_also_has_macros;

extern crate that_doesnt;

It seems like #[macro_use] applies to the whole paragraph, but if it were like this:

#[macro_use] extern crate that_defines_macros;
extern crate that_also_has_macros;

It would be much more obvious what the #[macro_use] actually does.

Comments are welcome.

[nrc]

The reasoning here is that #[macro_use] is just another attribute, Rustfmt doesn't distinguish between kinds of attributes. It seems strange to me to format one way for some attributes and some other way for others.

By the way, #[macro_use] is disappearing in the long run, so the decision here may be moot.

[joshtriplett]

I wouldn't have an objection if rustfmt had an option to single-line #[macro_use], but I don't think it should do so by default. I'd probably feel differently if we didn't plan to get rid of #[macro_use].

[nrc]

I propose closing this. We will keep the line break by default. Rustfmt might support an option for single line, but I don't think we should specify it.