NullnessFieldInvar.java

package fieldinvar;

import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.framework.qual.FieldInvariant;

public class NullnessFieldInvar {
    public class Super {
        public final @Nullable Object o;
        public @Nullable Object nonfinal = null;

        public Super(@Nullable Object o) {
            this.o = o;
        }
    }

    @FieldInvariant(field = "o", qualifier = NonNull.class)
    class Sub extends Super {
        public final @Nullable Object subO;

        public Sub(@NonNull Object o) {
            super(o);
            subO = null;
        }

        public Sub(@NonNull Object o, @Nullable Object subO) {
            super(o);
            this.subO = subO;
        }

        void test() {
            @NonNull Object x1 = this.o;
            @NonNull Object x2 = o;
            @NonNull Object x3 = super.o;
        }
    }

    class SubSub1 extends Sub {
        public SubSub1(@NonNull Object o) {
            super(o);
        }
    }

    @FieldInvariant(
        field = {"o", "subO"},
        qualifier = NonNull.class
    )
    class SubSub2 extends Sub {
        public SubSub2(@NonNull Object o) {
            super(o);
        }
    }

    class Use {
        void test(Super superO, Sub sub, SubSub1 subSub1, SubSub2 subSub2) {
            //:: error: (assignment.type.incompatible)
            @NonNull Object x1 = superO.o;
            @NonNull Object x2 = sub.o;
            @NonNull Object x3 = subSub1.o;

            //:: error: (assignment.type.incompatible)
            @NonNull Object x5 = sub.subO;
            //:: error: (assignment.type.incompatible)
            @NonNull Object x6 = subSub1.subO;
            @NonNull Object x7 = subSub2.subO;
        }
    }

    class SuperWithNonFinal {
        @Nullable Object nonfinal = null;
    }
    // nonfinal isn't final
    //:: error: (field.invariant.not.final)
    @FieldInvariant(field = "nonfinal", qualifier = NonNull.class)
    class SubSubInvalid extends SuperWithNonFinal {}

    // field is declared in this class
    //:: error: (field.invariant.not.found)
    @FieldInvariant(field = "field", qualifier = NonNull.class)
    class Invalid {
        final Object field = new Object();
    }

    @FieldInvariant(
        field = {"o", "subO"},
        qualifier = NonNull.class
    )
    class Shadowing extends SubSub2 {
        @Nullable Object o;
        @Nullable Object subO;

        void test() {
            //:: error: (assignment.type.incompatible)
            @NonNull Object x = o; // error
            //:: error: (assignment.type.incompatible)
            @NonNull Object x2 = subO; // error

            @NonNull Object x3 = super.o;
            @NonNull Object x4 = super.subO;
        }

        public Shadowing() {
            super("");
        }
    }

    //inherits: @FieldInvariant(field = {"o", "subO"}, qualifier = NonNull.class)
    class Inherits extends SubSub2 {
        @Nullable Object o;
        @Nullable Object subO;

        void test() {
            //:: error: (assignment.type.incompatible)
            @NonNull Object x = o; // error
            //:: error: (assignment.type.incompatible)
            @NonNull Object x2 = subO; // error

            @NonNull Object x3 = super.o;
            @NonNull Object x4 = super.subO;
        }

        public Inherits() {
            super("");
        }
    }

    class Super2 {}

    //:: error: (field.invariant.not.wellformed)
    @FieldInvariant(
        field = {},
        qualifier = NonNull.class
    )
    class Invalid1 extends Super2 {}
    //:: error: (field.invariant.not.wellformed)
    @FieldInvariant(
        field = {"a", "b"},
        qualifier = {NonNull.class, NonNull.class, NonNull.class}
    )
    class Invalid2 extends Super2 {}

    //:: error: (field.invariant.not.found)
    @FieldInvariant(field = "x", qualifier = NonNull.class)
    class NoSuper {}

    class SuperManyFields {
        public final @Nullable Object field1 = null;
        public final @Nullable Object field2 = null;
        public final @Nullable Object field3 = null;
        public final @Nullable Object field4 = null;
    }

    @FieldInvariant(
        field = {"field1", "field2", "field3", "field4"},
        qualifier = NonNull.class
    )
    class SubManyFields extends SuperManyFields {
        void test() {
            field1.toString();
            field2.toString();
            field3.toString();
            field4.toString();
        }
    }
}