Writing Eq::eq produces an unhelpful diagnostic (std::cmp::Eq cannot be made into an object)

[ExpHP]

fn hi() -> bool {
    Eq::eq(&(), &())
}

   Compiling playground v0.0.1 (file:///playground)
error[E0038]: the trait `std::cmp::Eq` cannot be made into an object
 --> src/main.rs:3:5
  |
3 |     Eq::eq(&(), &())
  |     ^^^^^^ the trait `std::cmp::Eq` cannot be made into an object
  |
  = note: the trait cannot use `Self` as a type parameter in the supertraits or where-clauses

error: aborting due to previous error

I stared at this for a moment in pure disbelief... and then once I woke up a bit more, I remembered that eq is actually on the PartialEq trait (and so what I wrote is not interpreted as <_ as Eq>::eq, but rather as <Eq>::eq).

[estebank]

Current output:

error[E0782]: trait objects must include the `dyn` keyword
 --> src/lib.rs:2:5
  |
2 |     Eq::eq(&(), &())
  |     ^^
  |
help: add `dyn` keyword before this trait
  |
2 |     <dyn Eq>::eq(&(), &())
  |     ++++   +

error[E0038]: the trait `Eq` cannot be made into an object
 --> src/lib.rs:2:5
  |
2 |     Eq::eq(&(), &())
  |     ^^ `Eq` cannot be made into an object
  |
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>)

The new error gives a hint to what's gonig on, but E0038 maybe should learn how to be clearer, as involving trait objects in fully qualified paths is somewhat uncommon and bound to be confusing every time.

[ExpHP]

I feel like there should maybe be a message specifically targeted to the case where the method belongs to a supertrait. Since I feel like the gotcha here is that Eq::eq looks just like Ord::cmp when it is actually not.

Or put another way, the issue isn't that the compiler mentions trait objects; rather, the issue is that it doesn't mention PartialEq.