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

public class FlowNegation {

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

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

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

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

    void testInvalidCase2() {
        String s = "m";
        // :: warning: (known.nonnull)
        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: (known.nonnull)
        Object m = (s != null) ? "m" : "n";
        s.toString();
    }

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

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

    void testTernaryInvalidCase2() {
        String s = "m";
        // :: warning: (known.nonnull)
        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.type.incompatible)
            @NonNull String l0 = s;
        } else {
        }
        // :: error: (assignment.type.incompatible)
        @NonNull String l1 = s;
    }
}