* @return {@code true} if so; {@code false} otherwise
     */
    static boolean isDeclarableByExtension(ConfigurationInternal configuration) {
        if (configuration.isCanBeDeclared()) {
            return true;
        } else {
            return configuration.getExtendsFrom().stream()
                    .map(ConfigurationInternal.class::cast)
                    .anyMatch(ci -> ci.isDeclarableByExtension());
        }
    }

            for (VariantIdentity identity : byIdentity.keySet()) {
                List<ConfigurationInternal> collisions = byIdentity.get(identity);
                if (collisions.size() > 1) {

                    ConfigurationInternal configuration = collisions.get(0);
                    List<ConfigurationInternal> filtered =
                        byIdentity.get(identity).stream()

        ConfigurationInternal configurationInternal = (ConfigurationInternal) configuration;
        Set<TaskProvider<COMPILE>> compileTasks = Cast.uncheckedCast(configurationToCompileTasks.computeIfAbsent(configurationInternal, key -> new HashSet<>()));
        compileTasks.add(compileTask);

    public void visitAll(Consumer<ConfigurationInternal> visitor) {
        visitor.accept(theOnlyConfiguration);
    }

    @Override
    public ConfigurationInternal findByName(String name) {
        if (name.equals(theOnlyConfiguration.getName())) {
            return theOnlyConfiguration;
        }
        return null;
    }

    public void setTheOnlyConfiguration(ConfigurationInternal theOnlyConfiguration) {

    }

    ConfigurationInternal consumable(String name, List<ConfigurationInternal> extendsFrom = []) {
        project.configurations.consumable(name) { conf ->
            extendsFrom.each { conf.extendsFrom(it) }
        }.get() as ConfigurationInternal
    }

    ConfigurationInternal resolvable(String name, List<ConfigurationInternal> extendsFrom = []) {

     */
    int size();

    boolean isFixedSize();

    Set<? extends ConfigurationInternal> getAll();

    void visitAll(Consumer<ConfigurationInternal> visitor);

    @Nullable
    ConfigurationInternal findByName(String name);

/**
 * Builds {@link LocalConfigurationMetadata} instances from {@link ConfigurationInternal}s, while
 * caching intermediary dependency and exclude state.
 */
@ServiceScope(Scope.Global.class)
public interface LocalConfigurationMetadataBuilder {

    LocalConfigurationGraphResolveMetadata create(
        ConfigurationInternal configuration,
        ConfigurationsProvider configurationsProvider,

    }

    @Override
    public Set<? extends ConfigurationInternal> getAll() {
        Set<? extends ConfigurationInternal> set = Cast.uncheckedCast(this);
        return ImmutableSet.copyOf(set);
    }

    @Override
    public void visitAll(Consumer<ConfigurationInternal> visitor) {
        for (Configuration configuration : this) {
            visitor.accept((ConfigurationInternal) configuration);
        }
    }

    private final Describable displayName;
    private final ConfigurationInternal clientConfiguration;

    public DefaultDependencyConstraintSet(Describable displayName, ConfigurationInternal clientConfiguration, DomainObjectSet<DependencyConstraint> backingSet) {
        super(backingSet);
        this.displayName = displayName;

     */
    @Override
    public Configuration verifyExistingConfigurationUsage(Configuration conf) {
        warnAboutReservedName();
        ConfigurationInternal internalConf = (ConfigurationInternal) conf;

        if (!getRole().isUsageConsistentWithRole(conf)) {
            warnAboutNeedToMutateUsage(internalConf);
            if (internalConf.usageCanBeMutated()) {