I get: [ts] 'Promise' only refers to a type, but is being used as a value here

Question

I'm taking an Angular2 course and following along. Everything I have been doing thus far for all the other exercise has worked fine until I got to creating this custom validator and this Promise code. Makes no sense to me why this would occur now.

I get: [ts] 'Promise' only refers to a type, but is being used as a value here.

Can't seem to resolve this. I get my error even without adding in the setTimeout function.

Per a suggestion from someone elsewhere. I added to the tsconfig.json: "compilerOptions": { ... "types" : [ "core-js" ] }

But I still get the error.

Using Visual Studio code: Version 1.10.1. OS: Windows 10 Pro.

Here's my code:

import {Control} from 'angular2/common';

export class UsernameValidators 
{
    static shouldBeUnique(control: Control) 
    {
       return new Promise((resolve, reject) =>
       {            
          setTimeout(function()
          {
             if (control.value == "Dan")
                resolve({ shouldBeUnique: true });
             else
                resolve(null);
          }, 1000);
       });
   }
}

Here's the course that I am taking and a screen shot of what I am being instructed to do. The intelliSense is different from mine. It works fine and they do not get the error I get.

Here's the courses end result.

Answer 1

You need to target ES6, or else use a polyfill library like bluebird. If you are targeting ES5 in the compiler output, then it will fail like this because ES5 has no Promises.