Doc comments are allowed on match arms

[simias]

A very minor issue but I noticed that rustc accepts to build code like this:

fn main() {
    match () {
        /// doc
        _ => (),
    };
}

I would expect an error at /// doc since there's no item to document here.

[alexchandel]

I would expect no error, just no documentation. Does rustdoc produce anything for this?

[simias]

@alexchandel The problem is that using /// where it doesn't make sense usually produces an error, for instance this won't compile:

fn main() {
    /// Say hello world
    println!("Hello, world!")
}

<anon>:2:5: 2:24 error: expected item after doc comment
<anon>:2     /// Say hello world
             ^~~~~~~~~~~~~~~~~~~

So it's not very coherent.

[sfackler]

It's parses because attributes are allowed on match arms, and /// foo desugars to #[doc = "foo"].

[steveklabnik]

Triage: no change

[estebank]

Current output:

warning: doc comment not used by rustdoc
 --> src/main.rs:3:9
  |
3 |         /// doc
  |         ^^^^^^^
  |
  = note: #[warn(unused_doc_comment)] on by default

[simias]

Sounds acceptable, should I close this? It was not a huge issue to begin with.