AssertAfter.java

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

public class AssertAfter {

    protected @Nullable String value;

    @EnsuresNonNull("value")
    public boolean setRepNonNull() {
        value = "";
        return true;
    }

    public void plain() {
        //:: error: (dereference.of.nullable)
        value.toString();
    }

    public void testAfter() {
        setRepNonNull();
        value.toString();
    }

    public void testBefore() {
        //:: error: (dereference.of.nullable)
        value.toString();
        setRepNonNull();
    }

    public void withCondition(@Nullable String t) {
        if (t == null) {
            setRepNonNull();
        }
        //:: error: (dereference.of.nullable)
        value.toString();
    }

    public void inConditionInTrue() {
        if (setRepNonNull()) {
            value.toString();
        } else {
            // nothing to do
        }
    }

    // skip-test: Come back when working on improved flow
    public void asCondition() {
        if (setRepNonNull()) {
        } else {
            value.toString(); // valid!
        }
    }
}

// Test that private fields can be mentioned in pre- and post-conditions.

class A {
    private @Nullable String privateField = null;

    @EnsuresNonNull("privateField")
    public void m1() {
        privateField = "hello";
    }

    @RequiresNonNull("privateField")
    public void m2() {}
}

class B {

    void f() {
        A a = new A();
        a.m1();
        a.m2();
    }
}