error[E0631]: type mismatch in function arguments
  --> $DIR/issue-60283.rs:17:13
   |
LL | pub fn foo<T, F>(_: T, _: F)
   |        --- required by a bound in this
...
LL |     F: for<'a> FnMut(<T as Trait<'a>>::Item),
   |                ----------------------------- required by this bound in `foo`
...
LL |     foo((), drop)
   |             ^^^^
   |             |
   |             expected signature of `fn(<() as Trait<'a>>::Item) -> _`
   |             found signature of `fn(()) -> _`

error[E0277]: the size for values of type `<() as Trait<'_>>::Item` cannot be known at compilation time
  --> $DIR/issue-60283.rs:17:13
   |
LL |     foo((), drop)
   |             ^^^^ doesn't have a size known at compile-time
   | 
  ::: $SRC_DIR/core/src/mem/mod.rs:LL:COL
   |
LL | pub fn drop<T>(_x: T) {}
   |             - required by this bound in `std::mem::drop`
   |
   = help: the trait `Sized` is not implemented for `<() as Trait<'_>>::Item`
help: consider further restricting the associated type
   |
LL | fn main() where <() as Trait<'_>>::Item: Sized {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0277, E0631.
For more information about an error, try `rustc --explain E0277`.