anchor.diff:    t.a();
     t.b();
     t.c();
  -}+}
  +
  +/**
  + *  I/flutter ( 1864): S.a
  +    I/flutter ( 1864): A.a
  +    I/flutter ( 1864): A2.a
  +    I/flutter ( 1864): A1.a
  +    I/flutter ( 1864): B.a
  +    I/flutter ( 1864): A.b
  +    I/flutter ( 1864): A2.b
  +    I/flutter ( 1864): A1.b
  +    I/flutter ( 1864): B.b
  +    I/flutter ( 1864): B.c
  + * */
positive.code:   }
  }
  
  class T = B with A, S;
  
  
  testMixins() {
  
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() {
  