import org.checkerframework.checker.initialization.qual.UnderInitialization;
import org.checkerframework.checker.nullness.qual.NonNull;

public class TypeFrames {

  class A {
    @NonNull String a;

    public A() {
      @UnderInitialization A l1 = this;
      // :: error: (assignment)
      @UnderInitialization(A.class) A l2 = this;
      a = "";
      @UnderInitialization(A.class) A l3 = this;
    }
  }

  interface I {}

  class B extends A implements I {
    @NonNull String b;

    public B() {
      super();
      @UnderInitialization(A.class) A l1 = this;
      // :: error: (assignment)
      @UnderInitialization(B.class) A l2 = this;
      b = "";
      @UnderInitialization(B.class) A l3 = this;
    }
  }

  // subtyping
  void t1(@UnderInitialization(A.class) B b1, @UnderInitialization(B.class) B b2) {
    @UnderInitialization(A.class) B l1 = b1;
    @UnderInitialization(A.class) B l2 = b2;
    // :: error: (assignment)
    @UnderInitialization(B.class) B l3 = b1;
  }
}