Make documentation clear about conditional compilation use

[Qantas94Heavy]

From what I read of the documentation, only whole items/modules/crates can be processed through conditional compilation.

Static entities in Rust — crates, modules and items — may have attributes applied to them.

Though this is not in the documentation, this seems to work:

fn main() {
    println!("{}", Blue as int);
    println!("{}", Green as int);
}

enum Color {
  Red = 0xff0000,
  #[cfg(windows)]
  Green = 0x00ff00,
  Blue = 0x0000ff
}

As expected, the compiler throws an error (on Linux):

<anon>:3:20: 3:25 error: unresolved name Green.

However, it's not clear in the documentation what is the scope of the attribute in this instance. Have I got my idea of what is an item wrong, or is this merely an oversight in the documentation?

[sfackler]

It's an oversight in the documentation. The set of placed attribute have been allowed has slowly expanded and the documentation hasn't kept up.

[steveklabnik]

Which documentation says this? I'd like to fix it.

[sfackler]

Looks like here @steveklabnik: http://doc.rust-lang.org/rust.html#attributes

[steveklabnik]

Ahh yes. The manual certainly needs lots of improvement. I'd welcome a fix to this section, if nobody else gets to it, I will at some point.