error[E0308]: mismatched types
  --> $DIR/fn-trait-formatting.rs:6:17
   |
LL |     let _: () = (box |_: isize| {}) as Box<dyn FnOnce(isize)>;
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found struct `std::boxed::Box`
   |
   = note: expected type `()`
              found type `std::boxed::Box<dyn std::ops::FnOnce(isize)>`

error[E0308]: mismatched types
  --> $DIR/fn-trait-formatting.rs:10:17
   |
LL |     let _: () = (box |_: isize, isize| {}) as Box<dyn Fn(isize, isize)>;
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found struct `std::boxed::Box`
   |
   = note: expected type `()`
              found type `std::boxed::Box<dyn std::ops::Fn(isize, isize)>`

error[E0308]: mismatched types
  --> $DIR/fn-trait-formatting.rs:14:17
   |
LL |     let _: () = (box || -> isize { unimplemented!() }) as Box<dyn FnMut() -> isize>;
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found struct `std::boxed::Box`
   |
   = note: expected type `()`
              found type `std::boxed::Box<dyn std::ops::FnMut() -> isize>`

error[E0277]: expected a `std::ops::Fn<(isize,)>` closure, found `{integer}`
  --> $DIR/fn-trait-formatting.rs:19:5
   |
LL |     needs_fn(1);
   |     ^^^^^^^^ expected an `Fn<(isize,)>` closure, found `{integer}`
   |
   = help: the trait `std::ops::Fn<(isize,)>` is not implemented for `{integer}`
note: required by `needs_fn`
  --> $DIR/fn-trait-formatting.rs:3:1
   |
LL | fn needs_fn<F>(x: F) where F: Fn(isize) -> isize {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.