import static org.gradle.api.internal.provider.Providers.notDefined

abstract class CollectionPropertySpec<C extends Collection<String>> extends PropertySpec<C> {
    AbstractCollectionProperty<String, C> propertyWithDefaultValue() {
        return property()
    }

    @Override
    AbstractCollectionProperty<String, C> propertyWithNoValue() {
        def p = property()
        p.set((List) null)
        return p
    }