title: Angular2 - Invalid provider for the NgModule only instances of Provider and Type are allowed
body: <p>I got this traceback and I can't replicate this error.</p>
  
  <pre><code>vendor.bundle.js:25942 
  Uncaught Error: Invalid provider for the NgModule 'NbSharedModule' 
  - only instances of Provider and Type are allowed, 
  got: [[object Object], MaterialDashboardProService, VehicleTypesService, ?undefined?, ...]
  </code></pre>
  
  <p>Here is my <code>NbSharedModule</code></p>
  
  <pre><code>import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
  import { CommonModule } from '@angular/common';
  import { ReactiveFormsModule, FormsModule } from '@angular/forms';
  import {MaterialModule} from '@angular/material';
  
  import { AdminFormComponent } from './admin-form/admin-form.component';
  import {
    MaterialDashboardProService,
    VehicleTypesService,
    LocationsService,
    VehiclesService,
    BookingsService,
    NotificationService,
    UsersService
  } from './services';
  import { OrganisationFormComponent } from './organisation-form/organisation-form.component';
  import {
    MdpActivatorDirective,
    MdpBootstrapSelectDirective,
    MdpDatetimePickerDirective,
    MdpTagsinputDirective
  } from './directives';
  import { ChunkPipe } from './pipes/chunk.pipe';
  import { VehicleTypesChooserComponent } from './vehicle-types-chooser/vehicle-types-chooser.component';
  import { VehicleCardComponent } from './vehicle-card/vehicle-card.component';
  import { LoaderComponent } from './loader/loader.component';
  import { NotificationComponent } from './notification/notification.component';
  import { TagsinputComponent } from './tagsinput/tagsinput.component';
  import { VehicleFormComponent } from './vehicle-form/vehicle-form.component';
  import { DeletePopupComponent } from './delete-popup/delete-popup.component';
  
  @NgModule({
    declarations: [
      OrganisationFormComponent,
      AdminFormComponent,
      MdpActivatorDirective,
      MdpDatetimePickerDirective,
      MdpBootstrapSelectDirective,
      MdpTagsinputDirective,
      ChunkPipe,
      VehicleTypesChooserComponent,
      VehicleCardComponent,
      LoaderComponent,
      NotificationComponent,
      TagsinputComponent,
      VehicleFormComponent,
      DeletePopupComponent
    ],
    imports: [
      CommonModule,
      ReactiveFormsModule,
      FormsModule,
      MaterialModule.forRoot()
    ],
    providers: [
      {provide: 'windowObject', useValue: window},
      MaterialDashboardProService,
      VehicleTypesService,
      LocationsService,
      VehiclesService,
      BookingsService,
      NotificationService,
      UsersService
    ],
    exports: [
      OrganisationFormComponent,
      AdminFormComponent,
      MdpActivatorDirective,
      MdpDatetimePickerDirective,
      MdpBootstrapSelectDirective,
      MdpTagsinputDirective,
      ChunkPipe,
      VehicleTypesChooserComponent,
      VehicleCardComponent,
      LoaderComponent,
      NotificationComponent,
      TagsinputComponent,
      VehicleFormComponent,
      DeletePopupComponent
    ],
    schemas: [CUSTOM_ELEMENTS_SCHEMA]
  })
  export class NbSharedModule { }
  </code></pre>
  
  <p><code>package.json</code></p>
  
  <pre><code>{
    "name": "foo-app",
    "version": "0.0.0",
    "license": "MIT",
    "angular-cli": {},
    "scripts": {
      "start": "ng serve",
      "lint": "tslint \"src/**/*.ts\"",
      "test": "ng test",
      "pree2e": "webdriver-manager update",
      "e2e": "protractor"
    },
    "private": true,
    "dependencies": {
      "@angular/common": "2.4.0",
      "@angular/compiler": "2.4.0",
      "@angular/core": "2.4.0",
      "@angular/forms": "2.4.0",
      "@angular/http": "2.4.0",
      "@angular/material": "^2.0.0-beta.1",
      "@angular/platform-browser": "2.4.0",
      "@angular/platform-browser-dynamic": "2.4.0",
      "@angular/router": "3.2.3",
      "@angular2-material/slide-toggle": "^2.0.0-alpha.8-2",
      "@types/jquery.datatables": "^1.10.34",
      "angular2-fullcalendar": "^1.1.1",
      "angular2-moment": "^1.0.0",
      "core-js": "^2.4.1",
      "rxjs": "5.0.0-beta.12",
      "ts-helpers": "^1.1.1",
      "zone.js": "^0.6.23"
    },
    "devDependencies": {
      "@angular/compiler-cli": "2.4.0",
      "@types/jasmine": "2.5.38",
      "@types/node": "^6.0.42",
      "angular-cli": "^1.0.0-beta.24",
      "codelyzer": "~2.0.0-beta.1",
      "jasmine-core": "2.5.2",
      "jasmine-spec-reporter": "2.5.0",
      "karma": "1.2.0",
      "karma-cli": "^1.0.1",
      "karma-jasmine": "^1.0.2",
      "karma-phantomjs-launcher": "^1.0.2",
      "karma-remap-istanbul": "^0.2.1",
      "protractor": "4.0.9",
      "ts-node": "1.2.1",
      "tslint": "^4.0.2",
      "typescript": "~2.0.3",
      "webdriver-manager": "10.2.5"
    }
  }
  </code></pre>