Protocol dispatch.swift

protocol A {
  func foo()
}
extension A {
  func foo() { print("A foo") }
  func bar() { print("A bar") }
}
protocol B: A {
  func bar()
}
extension B {
  func foo() { print("B foo") }
  func bar() { print("B bar") }
}

class C: B { }
let c: B = C()
print("Static type B:")
c.foo()  // prints "B foo"
c.bar()  // prints "B bar"
print("Static type A:")
(c as A).foo()  // prints "B foo"
(c as A).bar()  // prints "A bar" !!