CODEWITHSUNDEEP
scalatypes
Bogdan Vakulenko
Bogdan Vakulenko

Reputation: 3390

Type ranges in type member refinement

class Animal
class Cat extends Animal

trait ZPar {
  type K
  def get(i: K)
}

def zz(t:ZPar{ type K >: Animal } ) = {
   t.get(new Cat) //compiled! why?
}

This code compiles without errors, but I assumed that there must be an issue because K >: Animal and I'm passing Cat which is definitely not super type of Animal.

Is it something wrong with compiler or I just misunderstood the concept?

Upvotes: 0

Views: 40

Answers (2)

Dmytro Mitin
Dmytro Mitin

Reputation: 51683

It's not necessary that new Cat is of type Cat. new Cat can be not only of type Cat. It can be of types Cat, Animal, AnyRef or Any.

So here K is inferred to be minimal possible type, i.e. Animal.

Upvotes: 1

Alexey Romanov
Alexey Romanov

Reputation: 170805

An argument of t.get must have type t.K. The compiler doesn't know exactly what type that is, but it does know it's a supertype of Animal and therefore of Cat. So any value of type Cat has type t.K as well.

Upvotes: 1

Related Questions