How to make a function which is callable for &Foo and for <F : Foo>

help
2 
impl Foo {
    fn utility_shortcut(&self) {
        self.core_functionality();
    }
}

This makes the method available only on Foo trait objects, and that requires you to coerce to one in f2.

I can see a couple of approaches:

  1. Make utility_shortcut a free function that takes a &Foo trait object.
  2. Create a separate trait, let’s call it FooExt, that contains the util method. Then impl it for Foo and for F: Foo