Fun with extension-method-return-type overriding (port from Swift Sandbox)

override-method-return.swift

protocol Base { }
extension Base {
	var a: String? { return nil }
	var b: Int? { return nil }
}

protocol A: Base {
	var a: String { get }
}

protocol B: Base {
	var b: Int { get }
}

protocol All: A, B { }

struct Frag: B {
	let b: Int
}

print(Frag(b: 3).a)