producer.visitProducerTasks { assert false }
        producer.visitContentProducerTasks { assert false }
    }

    void assertHasKnownProducer(ProviderInternal<?> provider) {
        def producer = provider.producer
        assert producer.known
        producer.visitProducerTasks { assert false }
        producer.visitContentProducerTasks { assert false }
    }

        } else {
            return Value.missing();
        }
    }

    protected void beforeRead(@SuppressWarnings("unused") EvaluationContext.ScopeContext context) {
        provider.getProducer().visitContentProducerTasks(producer -> {
            if (!producer.getState().getExecuted()) {
                throw new InvalidUserCodeException(

            return value.asType();
        }
        return value.transform(transformer);
    }

    protected void beforeRead(EvaluationContext.ScopeContext context) {
        provider.getProducer().visitContentProducerTasks(producer -> {
            if (!producer.getState().getExecuted()) {
                throw new InvalidUserCodeException(

        default boolean isKnown() {
            return true;
        }

        void visitProducerTasks(Action<? super Task> visitor);

        default void visitContentProducerTasks(Action<? super Task> visitor) {
            visitProducerTasks(visitor);
        }

        default ValueProducer plus(ValueProducer producer) {
            if (this == NO_PRODUCER) {