title: An interface cannot be exported in an angular 2 module?
body: <p>I tried to export an interface in a NgModule-declaration and export and getting this error already in the editor (Visual Studio Code): <code>[ts] 'MyInterface' only refers to a type, but is being used as a value here.</code></p>
  
  <p>Here is the example code <strong>Edit-1</strong>:</p>
  
  <pre><code>import { NgModule }           from '@angular/core';
  import { CommonModule }       from '@angular/common';
  import { FormsModule }        from '@angular/forms';
  import { MaterialModule }     from '@angular/material';
  import { MyInterface }        from './my.interface';
  import { MyService }          from './my.service';
  
  @NgModule({
    imports:      [ CommonModule, FormsModule,  MaterialModule.forRoot()  ],
    declarations: [ MyInterface],//&lt;- this is causing the message
    exports:      [ MyInterface],
    providers:    [ MyService ]
  })
  export class MyModule { }
  </code></pre>
  
  <p>One part of an explanation I found <a href="https://stackoverflow.com/a/34850158/7564182">in the answer to this post</a>: "since interfaces are erased at runtime in TypeScript".
  I'm currently refactoring my app to feature modules, so I cannot test it right now: Can I use the interfaces only by import from './mypathto/my.interface'?</p>