DefaultAnnotation.java

import java.util.Iterator;
import java.util.List;
import org.checkerframework.checker.nullness.qual.*;
import org.checkerframework.framework.qual.DefaultQualifier;
import org.checkerframework.framework.qual.DefaultQualifiers;
import org.checkerframework.framework.qual.TypeUseLocation;

public class DefaultAnnotation {

    public void testNoDefault() {

        String s = null;
    }

    @DefaultQualifiers(
            @DefaultQualifier(
                value = org.checkerframework.checker.nullness.qual.NonNull.class,
                locations = {TypeUseLocation.ALL}
            ))
    public void testDefault() {

        //:: error: (assignment.type.incompatible)
        String s = null; // error
        List<String> lst = new List<String>(); // valid
        //:: error: (argument.type.incompatible)
        lst.add(null); // error
    }

    @DefaultQualifier(
        value = org.checkerframework.checker.nullness.qual.NonNull.class,
        locations = {TypeUseLocation.ALL}
    )
    public class InnerDefault {

        public void testDefault() {
            //:: error: (assignment.type.incompatible)
            String s = null; // error
            List<String> lst = new List<String>(); // valid
            //:: error: (argument.type.incompatible)
            lst.add(null); // error
            s = lst.get(0); // valid

            List<@Nullable String> nullList = new List<@Nullable String>(); // valid
            nullList.add(null); // valid
            //:: error: (assignment.type.incompatible)
            s = nullList.get(0); // error
        }
    }

    @DefaultQualifier(
        value = org.checkerframework.checker.nullness.qual.NonNull.class,
        locations = {TypeUseLocation.ALL}
    )
    public static class DefaultDefs {

        public String getNNString() {
            return "foo"; // valid
        }

        public String getNNString2() {
            //:: error: (return.type.incompatible)
            return null; // error
        }

        public <T extends @Nullable Object> T getNull(T t) {
            //:: error: (return.type.incompatible)
            return null; // invalid
        }

        public <T extends @NonNull Object> T getNonNull(T t) {
            //:: error: (return.type.incompatible)
            return null; // error
        }
    }

    public class DefaultUses {

        public void test() {

            DefaultDefs d = new DefaultDefs();

            @NonNull String s = d.getNNString(); // valid
        }

        @DefaultQualifier(
            value = org.checkerframework.checker.nullness.qual.NonNull.class,
            locations = {TypeUseLocation.ALL}
        )
        public void testDefaultArgs() {

            DefaultDefs d = new DefaultDefs();

            //:: error: (assignment.type.incompatible)
            String s1 = d.<@Nullable String>getNull(null); // error
            String s2 = d.<String>getNonNull("foo"); // valid
            //:: error: (type.argument.type.incompatible) :: error: (assignment.type.incompatible)
            String s3 = d.<@Nullable String>getNonNull("foo"); // error
        }
    }

    @DefaultQualifier(value = org.checkerframework.checker.nullness.qual.NonNull.class)
    static class DefaultExtends implements Iterator<String>, Iterable<String> {

        @Override
        public boolean hasNext() {
            throw new UnsupportedOperationException();
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }

        @Override
        public String next() {
            throw new UnsupportedOperationException();
        }

        @Override
        public Iterator<String> iterator() {
            return this;
        }
    }

    class List<E extends @Nullable Object> {
        public E get(int i) {
            throw new RuntimeException();
        }

        public boolean add(E e) {
            throw new RuntimeException();
        }
    }

    @DefaultQualifier(value = NonNull.class)
    public void testDefaultUnqualified() {

        //:: error: (assignment.type.incompatible)
        String s = null; // error
        List<String> lst = new List<String>(); // valid
        //:: error: (argument.type.incompatible)
        lst.add(null); // error
    }
}