Using `Foo::<Bar>` in some contexts where a type is expected gives wrong error message

[mcarton]

The following example gives a wrong error message:

fn main() {
    let f = foo.map(|a| a as Foo::<Bar>);
}

error: expected identifier, found `<`
 --> b.rs:2:35
  |
2 |     let f = foo.map(|a| a as Foo::<Bar>);
  |                                   ^

error: chained comparison operators require parentheses
 --> b.rs:2:35
  |
2 |     let f = foo.map(|a| a as Foo::<Bar>);
  |                                   ^^^^^^
  |
  = help: use `::<...>` instead of `<...>` if you meant to specify type arguments

error: expected expression, found `)`
 --> b.rs:2:40
  |
2 |     let f = foo.map(|a| a as Foo::<Bar>);
  |                                        ^

error: aborting due to 4 previous errors

The help: use ::<...>instead of<...>`` bit is wrong and suggests the opposite of the fix.

---

Note that none of the following give that error message:

fn main() {
    let g = a as Foo::<Bar>;
}

gives

error: expected identifier, found `<`
 --> b.rs:2:23
  |
2 |     let g = a as Foo::<Bar>;
  |                       ^

error: aborting due to previous error

and

fn main() {
    let g: Foo::<Bar>;
}

gives

error: expected identifier, found `<`
 --> b.rs:2:17
  |
2 |     let g: Foo::<Bar>;
  |                 ^

error: aborting due to previous error

which are correct but could be more explicit about the problem.

[GuillaumeGomez]

cc @jonathandturner