ices/51506.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#51506

#![feature(never_type)]
#![feature(specialization)]

use std::iter::{self, Empty};

trait Trait {
    type Out: Iterator<Item = u32>;

    fn f(&self) -> Option<Self::Out>;
}

impl<T> Trait for T {
    default type Out = !;

    default fn f(&self) -> Option<Self::Out> {
        None
    }
}

struct X;

impl Trait for X {
    type Out = Empty<u32>;

    fn f(&self) -> Option<Self::Out> {
        Some(iter::empty())
    }
}

fn f<T: Trait>(a: T) {
    if let Some(iter) = a.f() {
        println!("Some");
        for x in iter {
            println!("x = {}", x);
        }
    }
}

pub fn main() {
    f(10);
}

=== stdout ===
=== stderr ===
warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /home/runner/work/glacier/glacier/ices/51506.rs:2:12
  |
2 | #![feature(specialization)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information

error[E0277]: `!` is not an iterator
  --> /home/runner/work/glacier/glacier/ices/51506.rs:13:5
   |
7  |     type Out: Iterator<Item = u32>;
   |     ------------------------------- required by `Trait::Out`
...
13 |     default type Out = !;
   |     ^^^^^^^^^^^^^^^^^^^^^ `!` is not an iterator
   |
   = help: the trait `std::iter::Iterator` is not implemented for `!`

error: aborting due to previous error; 1 warning emitted

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