Scala: Call function only with specified path-dependent type param

Question

Lets have a class A with inner class.

class A {
    class InnerA
}

And class Test that holds instance of A

class Test(inst: A) {
    def someFun(p: inst.InnerA) {} //Neither A#InnerA, Nor inst.type#InnerA
}

Now i need to restrict someFun to be called only with parameter of type InnerA of specified inst (member of Test). (Not by any instance of InnerA that is achieved with A#InnerA)

val a: A = new A
val inna: a.InnerA = new a.InnerA
val test: Test = new Test(a)

But when i write this code:

test.someFun(inna)

type checker warns that "Type mismatch, expected: inst.type#InnerA, actual: a.InnerA"

Please suggest how can it be done.

---

Similar but NOT suitable solution is of form

def fun(a: A)(p: a.InnerA) {}

---

As for application: An A class is Enumeration class, and InnerA is Enumeration.Value class. And Test is a class i'd like to restrict to use with only specified Enumeration. And "inna" are instances of enumeration values that are constructed inside the Enumeration subclass.

Answer 1

With new Test(a) you lose the information that a becomes test.inst. For example, the following works:

class Test(val inst: A) {
  def someFun(p: inst.InnerA) = ()
}

val test: Test = new Test(new A)
val inna = new test.inst.InnerA
test.someFun(inna)