ConditionalNullness.java

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

public class ConditionalNullness {

    @EnsuresNonNullIf(
        expression = {"field", "method()"},
        result = true
    )
    boolean checkNonNull() {
        // don't bother with the implementation
        //:: error: (contracts.conditional.postcondition.not.satisfied)
        return true;
    }

    @Nullable Object field = null;

    @org.checkerframework.dataflow.qual.Pure
    @Nullable Object method() {
        return "m";
    }

    void testSelfWithCheck() {
        ConditionalNullness other = new ConditionalNullness();
        if (checkNonNull()) {
            field.toString();
            method().toString();
            //:: error: (dereference.of.nullable)
            other.field.toString(); // error
            //:: error: (dereference.of.nullable)
            other.method().toString(); // error
        }
        //:: error: (dereference.of.nullable)
        method().toString(); // error
    }

    void testSelfWithoutCheck() {
        //:: error: (dereference.of.nullable)
        field.toString(); // error
        //:: error: (dereference.of.nullable)
        method().toString(); // error
    }

    void testSelfWithCheckNegation() {
        if (checkNonNull()) {
            // nothing to do
        } else {
            //:: error: (dereference.of.nullable)
            field.toString(); // error
        }
        field.toString(); // error
    }

    void testOtherWithCheck() {
        ConditionalNullness other = new ConditionalNullness();
        if (other.checkNonNull()) {
            other.field.toString();
            other.method().toString();
            //:: error: (dereference.of.nullable)
            field.toString(); // error
            //:: error: (dereference.of.nullable)
            method().toString(); // error
        }
        //:: error: (dereference.of.nullable)
        other.method().toString(); // error
        //:: error: (dereference.of.nullable)
        method().toString(); // error
    }

    void testOtherWithoutCheck() {
        ConditionalNullness other = new ConditionalNullness();
        //:: error: (dereference.of.nullable)
        other.field.toString(); // error
        //:: error: (dereference.of.nullable)
        other.method().toString(); // error
        //:: error: (dereference.of.nullable)
        field.toString(); // error
        //:: error: (dereference.of.nullable)
        method().toString(); // error
    }

    void testOtherWithCheckNegation() {
        ConditionalNullness other = new ConditionalNullness();
        if (other.checkNonNull()) {
            // nothing to do
        } else {
            //:: error: (dereference.of.nullable)
            other.field.toString(); // error
            //:: error: (dereference.of.nullable)
            other.method().toString(); // error
            //:: error: (dereference.of.nullable)
            field.toString(); // error
        }
        //:: error: (dereference.of.nullable)
        field.toString(); // error
    }
}