inference.java

interface Config<C extends Config<C>> {
    C createCopy();
}

interface Factory<C extends Config<C>> {
}


class Registry {
    private static class Entry<C extends Config<C>> {
        static <C extends Config<C>> Entry<C> copyOf(Entry<C> entry) {
            return new Entry<>(entry.factory, entry.config.createCopy());
        }

        final Factory<C> factory;
        final C config;

        Entry(Factory<C> factory, C config) {
            this.factory = factory;
            this.config = config;
        }
    }

    private final List<Entry<? extends Config<?>>> entries;

    Registry() {
        this.entries = new CopyOnWriteArrayList<>();
    }

    Registry(List<Entry<? extends Config<?>>> entries) {
        this.entries = entries.stream()
                .map(Entry::copyOf)  // The type ExtensionRegistry.Entry does not define copyOf(ExtensionRegistry.Entry<capture#1-of ? extends ExtensionConfig<?>>) that is applicable here
                .collect(toCollection(CopyOnWriteArrayList::new));
    }
}