title: Compilation error in Angular
body: <pre><code>import { ModuleWithProviders } from '@angular/core';
  import { GlobalConfig } from './toastr-config';
  
  export declare class ToastrModule {
   error(arg0: any): any {
      throw new Error(&quot;Method not implemented.&quot;);
   };
   success(arg0: any): any {
      throw new Error(&quot;Method not implemented.&quot;);
   };
   setRootViewContainerRef(arg0: any): any {
      throw new Error(&quot;Method not implemented.&quot;);
   };
   constructor(parentModule: ToastrModule);
   static forRoot(config?: Partial&lt;GlobalConfig&gt;): ModuleWithProviders;
  }
  </code></pre>
  <p>Error</p>
  <blockquote>
  <p>ERROR in node_modules/ngx-toastr/toastr/toastr.module.d.ts(5,27): error TS1183: An implementation cannot be declared in ambient contexts.
  node_modules/ngx-toastr/toastr/toastr.module.d.ts(8,29): error TS1183: An implementation cannot be declared in ambient contexts.
  node_modules/ngx-toastr/toastr/toastr.module.d.ts(11,45): error TS1183: An implementation cannot be declared in ambient contexts.
  src/app/user/signup/signup.component.ts(40,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.
  src/app/user/signup/signup.component.ts(44,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.
  src/app/user/signup/signup.component.ts(47,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.
  src/app/user/signup/signup.component.ts(50,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.
  src/app/user/signup/signup.component.ts(53,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.
  src/app/user/signup/signup.component.ts(57,19): error TS2339: Property 'warning' does not exist on type 'ToastrModule'.</p>
  </blockquote>
  <br>
  <blockquote>
  <p>i ｢wdm｣: Failed to compile.</p>
  </blockquote>