title: Guice: Could not find a suitable constructor in com.twitter.inject.Injector
body: <p>I am using Guice injections and Finatra with my service. </p>
  
  <p>When trying to build a small test app I am getting this error:</p>
  
  <pre><code>Could not find a suitable constructor in com.twitter.inject.Injector. Classes must have either one (and only one) constructor annotated with @Inject or a zero-argument constructor that is not private. 
      at com.twitter.inject.Injector.class(Injector.scala:9)
  </code></pre>
  
  <p>My Module with the injectors looks like this</p>
  
  <pre><code>object ServiceModule extends TwitterModule {
  
    @Provides
    @Singleton
    def provideS2SAuthServiceConfig(): S2SAuthServiceConfig = {
      val servicePath = DynamicProperty.getInstance("myorg.module.auth.servicePath").getString
      val serviceUrl = DynamicProperty.getInstance("myorg.module.auth.serviceUrl").getString
  
      val httpClient: Service[Request, Response] = Http.client.withTls(serviceUrl).newService(serviceUrl)
  
      S2SAuthServiceConfig(httpClient, servicePath)
    }
  
    @Provides
    @Singleton
    def provideS2SAuthClient(injector: Injector): S2SAuthClient = {
      val s2sAuthClientClass = DynamicProperty.getInstance("myorg.mymodule.s2s.s2sAuthClient").getString
      val s2sAuthClientInstance = injector.instance(Class.forName(s2sAuthClientClass))
  
      s2sAuthClientInstance.asInstanceOf[S2SAuthClient]
    }
  }
  </code></pre>
  
  <p>It works well when I inject these objects in the constructor of my classes, but I get the error when trying to get an object instance like this:</p>
  
  <pre><code>def main (args: Array[String]): Unit = {
      val injector = new Injector(Guice.createInjector(ServiceModule))
      val authClient = injector.instance[S2SAuthClientImpl](classOf[S2SAuthClientImpl])
      val token = authClient.getToken("MyClientID", "MySecret", "MyScope")
      println(token)
    }
  </code></pre>
  
  <p>Any ideas why Guice is not able to find the constructor for the Twitter Injector class?</p>