a missing path separator (: instead of ::) in enum match leads to confusing error

[oconnor663]

enum Foo {
    Bar,
    Baz,
}

fn main() {
    let myfoo = Foo::Bar;
    match myfoo {
        Foo::Bar => {}
        Foo:Baz => {}  // OOPS: I forgot a colon here
    }
}

On the playground (rustc 1.53), here's what I see:

error: expected one of `=>`, `@`, `if`, or `|`, found `:`
  --> src/main.rs:10:12
   |
10 |         Foo:Baz => {}
   |            ^ expected one of `=>`, `@`, `if`, or `|`

It would be nice if rustc could say "hey it looks like you forgot a colon" here, similar to this case.

[oconnor663]

So fast! Thank you!