ERROR: Property 'then' does not exist on type 'Hero[]'

app.component.ts file ``` import { Component, OnInit } from '@angular/core'; import { Hero } from './hero'; import { HeroService } from './hero.service'; @Component({ selector: 'app-root', templateUrl: './app.component.html', styleUrls: ['./app.component.css'], providers: [HeroService] }) export class AppComponent implements OnInit{ title = 'Tour of Heroes'; heroes : Hero[ ]; selectedHero : Hero; constructor(private heroService: HeroService) { } getHeroes(): void { this.heroService.getHeroes().then(heroes => this.heroes = heroes); }; ngOnInit(): void { this.getHeroes(); }; onSelect(hero: Hero): void{ this.selectedHero = hero; }; } ``` hero.service.ts ``` import { Injectable } from '@angular/core'; import { Hero } from './hero'; import { HEROES } from './mock-heroes'; @Injectable() export class HeroService { getHeroes(): Promise<Hero[]> { return Promise.resolve(HEROES); } } ``` How to resolve this error?