Is a Path Dependent Type a subtype?

Question

trait A {
  trait B {
    def foo: A.this.B = new B{}
    def bar: A#B      = foo 
    def baz: A.this.B = bar // type mismatch; found : A#B required: A.this.B 
  }
         


        

Answer 1

In short: Yes it is

If you want, you can consider A#B to have an abstract reference to the containing A (and therefore not directly constructable, as for any abstract type), this reference being made concrete in the path-dependent subclasses.