How to understand `C.super[P]` in scala?

Question

I'm reading the book of "The depth of scala", and on chapter 6 "types", page 123:

The path C.super or C.super[P] where C refers to a class and P refers to a par- ent type of class C. Using the super keyword directly is shorthand for C.super. Use this path to disambiguate between identifiers defined on a class and a par- ent class.

I can't understand the C.super[P], why we can specify the type P after super?

I tried this scala code:

class P {
   def hello = "hello from P"
}

class C extends P {
  override  def hello = "hello from C"
}

class D extends C {
  override def hello = super[P].hello
}

val d = new D
d.hello

Which is unable to compile on this line:

  override def hello = super[P].hello

Answer 1

Note that P must be a parent type, not any supertype. I.e. if you have class D extends C with T1 with T2, and there is a hello method in class C and traits T1 and T2, just writing super.hello wouldn't tell the compiler which hello method you want. So you can write super[C].hello, super[T1].hello or super[T2].hello.