anchor.diff:    }
   }
   
  -class T = B with A, S;
  +class T = B with A1, A2, A, S;
   
   
   testMixins() {
  
positive.code:   t.a();
    t.b();
    t.c();
  }
negative.code:  */
  
  abstract class Base {
    a() {
  
    }
    b() {
  
    }
  }
  
  class S extends Base {
    a() {
      print("S.a");
      super.a();
    }
  }
  
  class A extends Base {
    a() {
      print("A.a");
      super.a();
    }
  
    b() {
      print("A.b");
      super.b();
    }
  }
  
  class A1 extends Base {
    a() {
      print("A1.a");
      super.a();
    }
  
    b() {
      print("A1.b");
      super.b();
    }
  }
  
  class A2 extends Base {
    a() {
      print("A2.a");
      super.a();
    }
  
    b() {
      print("A2.b");
      super.b();
    }
  }
  
  class B extends Base {
    a() {
      print("B.a");
      super.a();
    }
  
    b() {
      print("B.b");
      super.b();
    }
  
    c() {
  