to me protocol extensions are both cool and evil. cool as you can add code.
evil because it's more natural to add another declarations in those
extensions rather than implementation:
protocol Foo {
func foo()
}
extension Foo {
func bar() //*** natural assumption is that i can do this. but i can't
}
While this can indeed be a common mistake, it feels much less natural to do that once you think about what protocol conformances mean and what it would take to make it possible IMO.
