NAND.swift

protocol Bit {}
protocol IsSet {}
protocol IsClr {}

struct Set : Bit, IsSet {}
struct Clr : Bit, IsClr {}

protocol  Op { typealias Result }
extension Op { typealias Result = Set }

struct Nand<B0: Bit, B1: Bit> : Op {}
extension Nand where B0: IsSet, B1: IsSet {
  typealias Result = Clr
}
struct Not<B: Bit> {}
extension Not where B: IsSet {
  typealias Result = Clr
}
struct And<B0: Bit, B1: Bit> {
  typealias Result = Not<Nand<B0, B1>.Result>.Result
}
// ambiguous type name 'Result' in 'Nand<B0, B1>'


Nand<Clr, Clr>.Result.self
Nand<Clr, Set>.Result.self
Nand<Set, Clr>.Result.self
Nand<Set, Set>.Result.self