nightly.txt

error[E0308]: mismatched types
  --> src/main.rs:14:7
   |
14 |     a.f();
   |       ^ one type is more general than the other
   |
   = note: expected type `Trait`
              found type `Trait`

error[E0308]: mismatched types
  --> src/main.rs:32:13
   |
32 |     let x = <fn (&())>::make_g();
   |             ^^^^^^^^^^^^^^^^^^ one type is more general than the other
   |
   = note: expected type `X`
              found type `X`

error: aborting due to 2 previous errors

PR.txt

error: implementation of `Trait` is not general enough
  --> src/main.rs:14:7
   |
14 |     a.f();
   |       ^
   |
   = note: `Trait` would have to be implemented for the type `fn(&u8)`
   = note: but `Trait` is actually implemented for the type `for<'r> fn(&'r u8)`

error: implementation of `X` is not general enough
  --> src/main.rs:32:13
   |
32 |     let x = <fn (&())>::make_g();
   |             ^^^^^^^^^^^^^^^^^^
   |
   = note: `X` would have to be implemented for the type `for<'r> fn(&'r ())`
   = note: but `X` is actually implemented for the type `fn(&'0 ())`, for the specific lifetime `'0`

error: aborting due to 2 previous errors

test.rs

// 1
trait Trait {
    fn f(self);
}

impl<T> Trait for fn(&T) {
    fn f(self) {
        println!("f");
    }
}

fn main() {
    let a: fn(_) = |_: &u8| {};
    a.f();
}

// 2
trait X {
    type G;
    fn make_g() -> Self::G;
}

impl<'a> X for fn(&'a ()) {
    type G = &'a ();

    fn make_g() -> Self::G {
        &()
    }
}

fn higher_ranked_region_has_lost_its_binder() {
    let x = <fn (&())>::make_g();
}