The sample given at for `Writing-a-Language-Service-Plugin` doesn't compile.

Bug Report

🔎 Search Terms

plugin
language-service
compile

• I was unable to test this on prior versions because there are no earlier versions of the documentation_____

💻 Code

This is copied from the guide at
https://github.com/microsoft/TypeScript/wiki/Writing-a-Language-Service-Plugin

  const ts = modules.typescript;

  function create(info: ts.server.PluginCreateInfo) {
    // Set up decorator
    const proxy: ts.LanguageService = Object.create(null);
    for (let k of Object.keys(info.languageService) as Array<
      keyof ts.LanguageService
    >) {
      const x = info.languageService[k];
      proxy[k] = (...args: Array<{}>) => x.apply(info.languageService, args);
    }
    return proxy;
  }

  return { create };
}

🙁 Actual behavior

I am entering the code sample from https://github.com/microsoft/TypeScript/wiki/Writing-a-Language-Service-Plugin and I am getting compile errors while setting up the decorator:

🙂 Expected behavior

I was hoping I could copy/paste the sample and it would work.

NOTE: It's also possible the documentation around this just needs to be clearer. How do you go about starting the plugin? Do you run yo code? Do you run npm init? Do you just create a single file index.js? I am very unclear how to begin development of this plugin.