function createInjector(modulesToLoad) {
  var INSTANTIATING = {},
      providerSuffix = 'Provider',
      path = [],
      loadedModules = new HashMap(),
      providerCache = {
        $provide: {
            provider: supportObject(provider),
            factory: supportObject(factory),
            service: supportObject(service),
            value: supportObject(value),
            constant: supportObject(constant),
            decorator: decorator
          }
      },
      providerInjector = (providerCache.$injector =
          createInternalInjector(providerCache, function() {
            throw $injectorMinErr('unpr', "Unknown provider: {0}", path.join(' <- '));
          })),
      instanceCache = {},
      instanceInjector = (instanceCache.$injector =
          createInternalInjector(instanceCache, function(servicename) {
            var provider = providerInjector.get(servicename + providerSuffix);
            return instanceInjector.invoke(provider.$get, provider);
          }));


  forEach(loadModules(modulesToLoad), function(fn) { instanceInjector.invoke(fn || noop); });

  return instanceInjector;

  ////////////////////////////////////
  // $provider
  ////////////////////////////////////

  function supportObject(delegate) {
    return function(key, value) {
      if (isObject(key)) {
        forEach(key, reverseParams(delegate));
      } else {
        return delegate(key, value);
      }
    };
  }

  function provider(name, provider_) {
    assertNotHasOwnProperty(name, 'service');
    if (isFunction(provider_) || isArray(provider_)) {
      provider_ = providerInjector.instantiate(provider_);
    }
    if (!provider_.$get) {
      throw $injectorMinErr('pget', "Provider '{0}' must define $get factory method.", name);
    }
    return providerCache[name + providerSuffix] = provider_;
  }

  function factory(name, factoryFn) { return provider(name, { $get: factoryFn }); }

  function service(name, constructor) {
    return factory(name, ['$injector', function($injector) {
      return $injector.instantiate(constructor);
    }]);
  }

  function value(name, val) { return factory(name, valueFn(val)); }

  function constant(name, value) {
    assertNotHasOwnProperty(name, 'constant');
    providerCache[name] = value;
    instanceCache[name] = value;
  }

  function decorator(serviceName, decorFn) {
    var origProvider = providerInjector.get(serviceName + providerSuffix),
        orig$get = origProvider.$get;

    origProvider.$get = function() {
      var origInstance = instanceInjector.invoke(orig$get, origProvider);
      return instanceInjector.invoke(decorFn, null, {$delegate: origInstance});
    };
  }

  ////////////////////////////////////
  // Module Loading
  ////////////////////////////////////
  function loadModules(modulesToLoad){
    var runBlocks = [], moduleFn, invokeQueue, i, ii;
    forEach(modulesToLoad, function(module) {
      if (loadedModules.get(module)) return;
      loadedModules.put(module, true);

      try {
        if (isString(module)) {
          moduleFn = angularModule(module);
          runBlocks = runBlocks.concat(loadModules(moduleFn.requires)).concat(moduleFn._runBlocks);

          for(invokeQueue = moduleFn._invokeQueue, i = 0, ii = invokeQueue.length; i < ii; i++) {
            var invokeArgs = invokeQueue[i],
                provider = providerInjector.get(invokeArgs[0]);

            provider[invokeArgs[1]].apply(provider, invokeArgs[2]);
          }
        } else if (isFunction(module)) {
            runBlocks.push(providerInjector.invoke(module));
        } else if (isArray(module)) {
            runBlocks.push(providerInjector.invoke(module));
        } else {
          assertArgFn(module, 'module');
        }
      } catch (e) {
        if (isArray(module)) {
          module = module[module.length - 1];
        }
        if (e.message && e.stack && e.stack.indexOf(e.message) == -1) {
          // Safari & FF's stack traces don't contain error.message content
          // unlike those of Chrome and IE
          // So if stack doesn't contain message, we create a new string that contains both.
          // Since error.stack is read-only in Safari, I'm overriding e and not e.stack here.
          /* jshint -W022 */
          e = e.message + '\n' + e.stack;
        }
        throw $injectorMinErr('modulerr', "Failed to instantiate module {0} due to:\n{1}",
                  module, e.stack || e.message || e);
      }
    });
    return runBlocks;
  }

  ////////////////////////////////////
  // internal Injector
  ////////////////////////////////////

  function createInternalInjector(cache, factory) {

    function getService(serviceName) {
      if (cache.hasOwnProperty(serviceName)) {
        if (cache[serviceName] === INSTANTIATING) {
          throw $injectorMinErr('cdep', 'Circular dependency found: {0}', path.join(' <- '));
        }
        return cache[serviceName];
      } else {
        try {
          path.unshift(serviceName);
          cache[serviceName] = INSTANTIATING;
          return cache[serviceName] = factory(serviceName);
        } finally {
          path.shift();
        }
      }
    }

    function invoke(fn, self, locals){
      var args = [],
          $inject = annotate(fn),
          length, i,
          key;

      for(i = 0, length = $inject.length; i < length; i++) {
        key = $inject[i];
        if (typeof key !== 'string') {
          throw $injectorMinErr('itkn',
                  'Incorrect injection token! Expected service name as string, got {0}', key);
        }
        args.push(
          locals && locals.hasOwnProperty(key)
          ? locals[key]
          : getService(key)
        );
      }
      if (!fn.$inject) {
        // this means that we must be an array.
        fn = fn[length];
      }


      // Performance optimization: http://jsperf.com/apply-vs-call-vs-invoke
      switch (self ? -1 : args.length) {
        case  0: return fn();
        case  1: return fn(args[0]);
        case  2: return fn(args[0], args[1]);
        case  3: return fn(args[0], args[1], args[2]);
        case  4: return fn(args[0], args[1], args[2], args[3]);
        case  5: return fn(args[0], args[1], args[2], args[3], args[4]);
        case  6: return fn(args[0], args[1], args[2], args[3], args[4], args[5]);
        case  7: return fn(args[0], args[1], args[2], args[3], args[4], args[5], args[6]);
        case  8: return fn(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7]);
        case  9: return fn(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7],
          args[8]);
        case 10: return fn(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7],
          args[8], args[9]);
        default: return fn.apply(self, args);
      }
    }

    function instantiate(Type, locals) {
      var Constructor = function() {},
          instance, returnedValue;

      // Check if Type is annotated and use just the given function at n-1 as parameter
      // e.g. someModule.factory('greeter', ['$window', function(renamed$window) {}]);
      Constructor.prototype = (isArray(Type) ? Type[Type.length - 1] : Type).prototype;
      instance = new Constructor();
      returnedValue = invoke(Type, instance, locals);

      return isObject(returnedValue) || isFunction(returnedValue) ? returnedValue : instance;
    }

    return {
      invoke: invoke,
      instantiate: instantiate,
      get: getService,
      annotate: annotate,
      has: function(name) {
        return providerCache.hasOwnProperty(name + providerSuffix) || cache.hasOwnProperty(name);
      }
    };
  }
}
@ngdoc method
@name AUTO.$provide#decorator
@methodOf AUTO.$provide
@description

Register a **service decorator** with the {@link AUTO.$injector $injector}. A service decorator
intercepts the creation of a service, allowing it to override or modify the behaviour of the
service. The object returned by the decorator may be the original service, or a new service
object which replaces or wraps and delegates to the original service.

@param {string} name The name of the service to decorate.
@param {function()} decorator This function will be invoked when the service needs to be
   instantiated and should return the decorated service instance. The function is called using
   the {@link AUTO.$injector#invoke injector.invoke} method and is therefore fully injectable.
   Local injection arguments:

   * `$delegate` - The original service instance, which can be monkey patched, configured,
     decorated or delegated to.

@example
Here we decorate the {@link ng.$log $log} service to convert warnings to errors by intercepting
calls to {@link ng.$log#error $log.warn()}.
<pre>
  $provider.decorator('$log', ['$delegate', function($delegate) {
    $delegate.warn = $delegate.error;
    return $delegate;
  }]);
</pre>