warning: cast `foo` with `as *const fn() -> _` to use it as a pointer
  --> $DIR/function-references.rs:7:23
   |
LL |     println!("{:p}", &foo);
   |                       ^^^
   |
   = note: `#[warn(function_references)]` on by default

warning: cast `bar` with `as *const fn(_) -> _` to use it as a pointer
  --> $DIR/function-references.rs:9:23
   |
LL |     println!("{:p}", &bar);
   |                       ^^^

warning: cast `baz` with `as *const fn(_, _) -> _` to use it as a pointer
  --> $DIR/function-references.rs:11:23
   |
LL |     println!("{:p}", &baz);
   |                       ^^^

warning: 3 warnings emitted