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

public class FlowNegation {

  void testSimpleValid() {
    String s = "m";
    s.toString();
  }

  void testCase1() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    if (s != null) {
    } else {
      // nothing to do
    }
    s.toString();
  }

  void testCase2() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    if (s == null) {
    } else {
      // nothing to do
    }
    s.toString();
  }

  void testInvalidCase1() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    if (s != null) {
      s = null;
    } else {
      // nothing to do
    }
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  void testInvalidCase2() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    if (s != null) {
      // nothing to do
    } else {
      s = null;
    }
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  void testSimpleValidTernary() {
    String s = "m";
    s.toString();
  }

  void testTernaryCase1() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    Object m = (s != null) ? "m" : "n";
    s.toString();
  }

  void testTernaryCase2() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    Object m = (s == null) ? "m" : "n";
    s.toString();
  }

  void testTernaryInvalidCase1() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    Object m = (s != null) ? (s = null) : "n";
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  void testTernaryInvalidCase2() {
    String s = "m";
    // :: warning: (nulltest.redundant)
    Object m = (s != null) ? "m" : (s = null);
    // :: error: (dereference.of.nullable)
    s.toString(); // error
  }

  void testAssignInCond() {
    String s = "m";
    if ((s = null) != "m") {
      // :: error: (assignment)
      @NonNull String l0 = s;
    } else {
    }
    // :: error: (assignment)
    @NonNull String l1 = s;
  }
}