error[E0277]: the size for values of type `(dyn Fn() -> Fut + 'static)` cannot be known at compilation time
  --> $DIR/dont-elaborate-non-self.rs:7:11
   |
LL | fn f<Fut>(a: dyn F<Fut>) {}
   |           ^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `(dyn Fn() -> Fut + 'static)`
   = help: unsized fn params are gated as an unstable feature
help: you can use `impl Trait` as the argument type
   |
LL | fn f<Fut>(a: impl F<Fut>) {}
   |              ~~~~
help: function arguments must have a statically known size, borrowed types always have a known size
   |
LL | fn f<Fut>(a: &dyn F<Fut>) {}
   |              +

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.