error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
  --> $DIR/type-alias-impl-trait-fn-type.rs:6:20
   |
LL | type Foo = fn() -> impl Send;
   |                    ^^^^^^^^^
   |
   = note: `impl Trait` is only allowed in arguments and return types of functions and methods

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0562`.