message: test closure-to-fn-ptr coercions a bit more
diff: @@ -5,7 +5,8 @@ static FOO: fn() = || { assert_ne!(42, 43) };
  static BAR: fn(i32, i32) = |a, b| { assert_ne!(a, b) };
  // use to first make the closure FnOnce() before making it fn()
  -fn magic<F: FnOnce()>(f: F) -> F { f }
  +fn magic0<R, F: FnOnce() -> R>(f: F) -> F { f }
  +fn magic1<T, R, F: FnOnce(T) -> R>(f: F) -> F { f }
  fn main() {
  FOO();
  @@ -15,6 +16,20 @@ fn main() {
  let boo: &dyn Fn(i32, i32) = &BAR;
  boo(48, 49);
  - let f = magic(||{}) as fn();
  + let f: fn() = ||{};
  f();
  + let f = magic0(||{}) as fn();
  + f();
  +
  + let g: fn(i32) = |i| assert_eq!(i, 2);
  + g(2);
  + let g = magic1(|i| assert_eq!(i, 2)) as fn(i32);
  + g(2);
  +
  + // FIXME: This fails with "invalid use of NULL pointer"
  + //let h: fn() -> ! = || std::process::exit(0);
  + //h();
  + // FIXME: This does not even compile?!?
  + //let h = magic0(|| std::process::exit(0)) as fn() -> !;
  + //h();
  }
  