Tried to find bootstrap code,but could not. Specify either statically analyzable bootstrap code or pass in an entryModule to the plugins options.

proxy.conf.json

{
  "/api": {
    "target": "http://127.0.0.1:3000","secure": false
  }
}

主polymer.ts

document.addEventListener('WebComponentsReady',() => {
  require('./main.ts');
});

main.ts

import './polyfills.ts';

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { environment } from './environments/environment';
import { AppModule } from './app/';

if (environment.production) {
  enableProdMode();
}

// platformBrowserDynamic().bootstrapModule(AppModule);
platformBrowserDynamic().bootstrapModule(AppModule);

我该怎么纠正？