title: Typescript Cannot use 'new' with an expression whose type lacks a call or construct signature
body: <p>I'm trying to create a sharepoint webpart using the new sharepoint framework, which uses the microsoft graph
  <a href="https://dev.office.com/sharepoint/docs/spfx/web-parts/guidance/call-microsoft-graph-from-your-web-part" rel="nofollow noreferrer">as shown here:</a></p>
  
  <p>Here is a sample that I am using for <a href="https://github.com/SharePoint/sp-dev-fx-webparts/tree/master/samples/react-aad-implicitflow" rel="nofollow noreferrer">reference</a>.</p>
  
  <p>I created a new project using the yeoman generator for sharepoint.</p>
  
  <p>Installed adal: npm install adal-angular</p>
  
  <p>Installed typings for adal: typings install adal --source dt --global --save</p>
  
  <p>Copied the relevant parts from the WebPart.tsx file:</p>
  
  <pre><code>const AuthenticationContext = require('adal-angular');
  import adalConfig from '../AdalConfig';
  import { IAdalConfig } from '../../IAdalConfig';
  import '../../WebPartAuthenticationContext';
  
  export default class ReactClient extends React.Component&lt;IReactClientProps, IReactClientState&gt; {
    private authCtx: adal.AuthenticationContext;
  
    constructor(props: IReactClientProps, state: IReactClientState) {
      super(props);
    }
  
  this.state = {
    loading: false,
    error: null,
    signedIn: false
  };
  
  const config: IAdalConfig = adalConfig;
  config.popUp = true;
  config.webPartId = this.props.webPartId;
  config.callback = (error: any, token: string): void =&gt; {
    this.setState((previousState: IReactClientState, currentProps: IReactClientProps): IReactClientState =&gt; {
      previousState.error = error;
      previousState.signedIn = !(!this.authCtx.getCachedUser());
      return previousState;
    });
  };
  
  this.authCtx = new AuthenticationContext(config);
  AuthenticationContext.prototype._singletonInstance = undefined;
  </code></pre>
  
  <p>}</p>
  
  <p>The line:</p>
  
  <pre><code>private authCtx: adal.AuthenticationContext;
  </code></pre>
  
  <p>has no problem identifying the namespace adal that is created in the adal type file. </p>
  
  <p>However, the line:</p>
  
  <pre><code>this.authCtx = new AuthenticationContext(config);
  </code></pre>
  
  <p>gives me the error: Cannot use 'new' with an expression whose type lacks a call or construct signature</p>
  
  <p>The constructor is there in the adal type file. I don't see what's missing. I'm hoping one of you guys can shed some light on it for me.</p>
  
  <p>Thanks, </p>