}
        stack.addFirst(new ScopeState());
    }

    private ScopeState getScopeState() {
        LinkedList<ScopeState> stack = values.get();
        if (stack == null || stack.isEmpty()) {
            throw new IllegalStateException();
        }
        return stack.getFirst();
    }

    public void exit() throws MojoExecutionException {
        final LinkedList<ScopeState> stack = values.get();

        public Collection<CachingProvider<?>> providers() {
            return provided.values();
        }
    }

    private final List<ScopeState> values = new CopyOnWriteArrayList<>();

    public void enter() {
        values.add(0, new ScopeState());
    }

    protected ScopeState getScopeState() {
        if (values.isEmpty()) {
            throw new OutOfScopeException("Cannot access session scope outside of a scoping block");