title: 'mat-slide-toggle' is not a known element after import
body: <p>I'm trying to use <code>&lt;mat-slide-toggle&gt;Click me!&lt;/mat-slide-toggle&gt;</code>inside a component which already has <code>MatSlideToggleModule</code> imported, but I'm still getting the message that it's not a known element.</p>
  
  <p><em>Angular version: 8.0.1</em></p>
  
  <p><strong>HTML Page (slide-page.html)</strong></p>
  
  <pre><code>&lt;div class="grid-slide-toggle-material"&gt; 
    &lt;mat-slide-toggle&gt;Click me!&lt;/mat-slide-toggle&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p><strong>Module (slide-page.module.ts)</strong></p>
  
  <pre><code>import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core'; 
  import { CommonModule } from '@angular/common';
  import { MaterialModule } from 'projects/authenticator/src/shared/modules/material.module';
  import { BasicModule } from 'src/app/shared/modules/basic/basic.module';
  import { MatButtonToggleModule, MatButtonToggleGroup } from '@angular/material';
  import { MatSlideToggleModule } from '@angular/material/slide-toggle';
  import { ReactiveFormsModule, FormsModule } from '@angular/forms';
  
  @NgModule({
    declarations: [],
    imports: [
      MaterialModule,
      ReactiveFormsModule,
      CommonModule,
      FormsModule,
      MatButtonToggleModule,
      MatSlideToggleModule 
    ]
  })
  export class SlidePageModule { }
  </code></pre>
  
  <p>How is it possible that the html is not being recognized even after the imports in the item's module?</p>