namespace A
{
  public struct KeyValuePair[X,Y]
  {
    public this (_ : X, _ :  Y)
    { }
  }

  public interface IComparer[T]
  {
     Compare (_ : T) : int;
  }

  public class KeyValuePairComparer[K,V] : IComparer[KeyValuePair[K,V]]
  {
    public Compare (_ : KeyValuePair[K,V]) :  int
    {
       0;
    }
  }

  public class TreeBag[T]
  {
     mutable  comparer : IComparer[T];

    public this (mutable  comparer : IComparer[T])
    {
      this.comparer = comparer;
    }

    public Find (mutable  item : ref T) :  int
    {
       comparer.Compare (item);
    }
  }

  public class X
  {
    public static Test () :  void
    {
      mutable  pair =  KeyValuePair (3, 89);
      mutable  comparer =  KeyValuePairComparer ();
      mutable  bag =  TreeBag (comparer);
      _ = bag.Find (ref pair);
    }
  }
}

namespace B
{
  public class KeyValuePair[X,Y]
  {
    public this (_ : X, _ :  Y)
    { }
  }

  public interface IComparer[T]
  {
     Compare (_ : T) : int;
  }

  public class KeyValuePairComparer[K,V] : IComparer[KeyValuePair[K,V]]
  {
    public Compare (_ : KeyValuePair[K,V]) :  int
    {
       0;
    }
  }

  public class TreeBag[T]
  {
     mutable  comparer : IComparer[T];

    public this (mutable  comparer : IComparer[T])
    {
      this.comparer = comparer;
    }

    public Find (mutable  item : ref T) :  int
    {
       comparer.Compare (item);
    }
  }

  public class X
  {
    public static Test () :  void
    {
      mutable  pair =  KeyValuePair (3, 89);
      mutable  comparer =  KeyValuePairComparer ();
      mutable  bag =  TreeBag (comparer);
      _ = bag.Find (ref pair);
    }
  }
}

class X
{
  static Main () :  void
  {
    A.X.Test ();
    B.X.Test ();
  }
}
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