scala - Scala では型が等しくないという証拠

Question

2 つの型が等しくないことが証明された場合にのみ意味をなすように、メソッドを制約する方法はありますか?

trait Something[A, B] {
  // I can only be called if type A is the same as type B
  def ifEqual(implicit ev: A =:= B)

  // Now I cannot be called if type A is proven to be the same as type B
  def ifNotEqual(implicit ev: A ??? B)
}

Answer 1

はい。形のないものから、

// Type inequalities
trait =:!=[A, B] 

implicit def neq[A, B] : A =:!= B = new =:!=[A, B] {}
implicit def neqAmbig1[A] : A =:!= A = ???
implicit def neqAmbig2[A] : A =:!= A = ???