checker/tests/nullness/Issue306.java

// Test case for Issue 306:
// https://github.com/typetools/checker-framework/issues/306

// @skip-test until the issue is fixed

import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

public class Issue306 {
  @MonotonicNonNull Object x;

  static <T> T check(T var) {
    return var;
  }

  void fakeMethod() {
    // @MonotonicNonNull is not reflexive.
    // However, it is the most specific type argument inferred for check. Therefore, an error is
    // raised.
    // We need a mechanism to not consider a qualifier in type inference.
    check(x);

    // Ugly way around the problem:
    Issue306.<@Nullable Object>check(x);

    // The following error has to be raised: from the signature it is not guaranteed that the
    // parameter is returned.
    // :: error: (monotonic)
    x = check(x);
  }

  @MonotonicNonNull Object y;

  void realError(@MonotonicNonNull Object p) {
    // :: error: (monotonic)
    x = y;
    // :: error: (monotonic)
    x = p;
    // It would be nice not to raise the following error.
    // :: error: (monotonic)
    x = x;
  }
}