void removeMutationValidator(MutationValidator validator);

    /**
     * Visits the variants of this configuration.
     */
    void collectVariants(VariantVisitor visitor);

    boolean isCanBeMutated();

    /**
     * Gets the complete set of exclude rules including those contributed by
     * superconfigurations.
     */
    Set<ExcludeRule> getAllExcludeRules();

    /**

            if (getShowingAllVariants().get()) {
                ConfigurationInternal configurationInternal = (ConfigurationInternal) configuration;
                if (!configurationInternal.isCanBeMutated()) {
                    throw new IllegalStateException(
                        "The configuration '" + configuration.getName() + "' is not mutable. " +

        return outgoing;
    }

    @Override
    public void collectVariants(VariantVisitor visitor) {
        outgoing.collectVariants(visitor);
    }

    @Override
    public boolean isCanBeMutated() {
        boolean immutable = observed || currentResolveState.get().isPresent();
        return !immutable;
    }

    @Override
    public void markAsObserved() {
        if (observed) {