checker/tests/fenum/TestInstance.java

import org.checkerframework.checker.fenum.qual.Fenum;

@SuppressWarnings("fenum:assignment")
public class TestInstance {
  public final @Fenum("A") Object ACONST1 = new Object();
  public final @Fenum("A") Object ACONST2 = new Object();
  public final @Fenum("A") Object ACONST3 = new Object();

  public final @Fenum("B") Object BCONST1 = new Object();
  public final @Fenum("B") Object BCONST2 = new Object();
  public final @Fenum("B") Object BCONST3 = new Object();
}

class FenumUserTestInstance {
  @Fenum("A") Object state1 = new TestInstance().ACONST1;

  // :: error: (assignment)
  @Fenum("B") Object state2 = new TestInstance().ACONST1;

  void foo(TestInstance t) {
    // :: error: (assignment)
    state1 = new Object();

    state1 = t.ACONST2;
    state1 = t.ACONST3;

    // :: error: (assignment)
    state1 = t.BCONST1;

    // :: error: (method.invocation)
    state1.hashCode();
    // :: error: (method.invocation)
    t.ACONST1.hashCode();

    // sanity check: unqualified instantiation and call work.
    Object o = new Object();
    o.hashCode();

    if (t.ACONST1 == t.ACONST2) {}

    // :: error: (binary)
    if (t.ACONST1 == t.BCONST2) {}
  }
}