GenericsExample.java

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

// This is the example from manual section:
// "Generics (parametric polymorphism or type polymorphism)"
// whose source code is ../../../docs/manual/advanced-features.tex
class GenericsExample {

    class MyList1<@Nullable T> {
        T t;
        @Nullable T nble;
        @NonNull T nn;

        MyList1(T t, @Nullable T nble, @NonNull T nn) {
            this.t = t;
            this.nble = nble;
            this.nn = nn;
        }

        void add(T arg) {}

        T get(int i) {
            return t;
        }

        void m() {
            t = null;
            t = nble;
            nble = null;
            //:: error: (assignment.type.incompatible)
            nn = null;
            t = this.get(0);
            nble = this.get(0);
            //:: error: (assignment.type.incompatible)
            nn = this.get(0);
            this.add(t);
            this.add(nble);
            this.add(nn);
        }
    }

    class MyList1a<@Nullable T extends @Nullable Object> {
        T t;
        @Nullable T nble;
        @NonNull T nn;

        MyList1a(T t, @Nullable T nble, @NonNull T nn) {
            this.t = t;
            this.nble = nble;
            this.nn = nn;
        }

        void add(T arg) {}

        T get(int i) {
            return t;
        }

        void m() {
            t = null;
            t = nble;
            nble = null;
            //:: error: (assignment.type.incompatible)
            nn = null;
            t = this.get(0);
            nble = this.get(0);
            //:: error: (assignment.type.incompatible)
            nn = this.get(0);
            this.add(t);
            this.add(nble);
            this.add(nn);
        }
    }

    class MyList2<@NonNull T extends @NonNull Object> {
        T t;
        @Nullable T nble;
        @NonNull T nn;

        MyList2(T t, @Nullable T nble, @NonNull T nn) {
            this.t = t;
            this.nble = nble;
            this.nn = nn;
        }

        void add(T arg) {}

        T get(int i) {
            return t;
        }

        void m() {
            //:: error: (assignment.type.incompatible)
            t = null;
            //:: error: (assignment.type.incompatible)
            t = nble;
            nble = null;
            //:: error: (assignment.type.incompatible)
            nn = null;
            t = this.get(0);
            nble = this.get(0);
            nn = this.get(0);
            this.add(t);
            //:: error: (argument.type.incompatible)
            this.add(nble);
            this.add(nn);
        }
    }

    class MyList2a<T extends @NonNull Object> { // same as MyList2
        T t;
        @Nullable T nble;
        @NonNull T nn;

        MyList2a(T t, @Nullable T nble, @NonNull T nn) {
            this.t = t;
            this.nble = nble;
            this.nn = nn;
        }

        void add(T arg) {}

        T get(int i) {
            return t;
        }

        void m() {
            //:: error: (assignment.type.incompatible)
            t = null;
            //:: error: (assignment.type.incompatible)
            t = nble;
            nble = null;
            //:: error: (assignment.type.incompatible)
            nn = null;
            t = this.get(0);
            nble = this.get(0);
            nn = this.get(0);
            this.add(t);
            //:: error: (argument.type.incompatible)
            this.add(nble);
            this.add(nn);
        }
    }

    class MyList3<T extends @Nullable Object> {
        T t;
        @Nullable T nble;
        @NonNull T nn;

        MyList3(T t, @Nullable T nble, @NonNull T nn) {
            this.t = t;
            this.nble = nble;
            this.nn = nn;
        }

        void add(T arg) {}

        T get(int i) {
            return t;
        }

        void m() {
            //:: error: (assignment.type.incompatible)
            t = null;
            //:: error: (assignment.type.incompatible)
            t = nble;
            nble = null;
            //:: error: (assignment.type.incompatible)
            nn = null;
            t = this.get(0);
            nble = this.get(0);
            //:: error: (assignment.type.incompatible)
            nn = this.get(0);
            this.add(t);
            //:: error: (argument.type.incompatible)
            this.add(nble);
            this.add(nn);
        }
    }
}