Type declaration in interfaces?

[Henning Hasemann]

Say I would want to write a few templated container classes (for example
a set, a linked list, a heap, etc. which all implement an
interface Container which looks like this:

interface Container(T) {
  void insert(T);
  void remove(Iterator!(T));
  size_t length();
}

(Please no comments about the usefullness of the interface and classes
itself, they are just examples!)

You already see the problem here: Iterator.
Well Iterator actually might be defined like this:

interface Iterator(T) {
  T content();
}

But the real problem is: Each container class will have its own
iterator implementation and remove() should only be defined
for exactly that implementation.
I could do it like this:

class Set(T) : Container(T) {
  void remove(Iterator!(T) it) {
    if(cast(SetIterator)it !is null) {
     // actually do anything
    }
    else
     // runtime fault
  }
}

But I'd prefer to do it at compile time somehow. Here an imaginary example
which is not syntactically D but should explain what I want:

// ------

interface ItBase(T) {
  T content();
}

interface Container(T) {
  // Means: whatever wants to implement this interface
  // has to define a type named "Iterator" which in turn
  // implements ItBase
  type Iterator(T) : ItBase(T);
  void insert(T);
  // Return iterator to some item, this will be the "first"
  // item on ordered containers
  Iterator!(T) getIterator();
  // Uses the Iterator declared with "type"
  void remove(Iterator!(T));
  size_t length();
}

class Set(T) : Container(T) {
  static class Iterator(T) : ItBase(T) {
    // TODO: Write a set-specific iterator
  }
  // TODO: Implement Container methods plus some more
}

Container(int) c = new Set(int);
c.insert(5);
c.insert(6);
auto it = c.getIterator();
c.remove(it);


Any ideas how to do this?

TIA
Henning