How can I silence the TS2354 error message in TypeScript 2.1.4?

Question

I am getting error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found. on my webpack 2 build using the new importHelpers option of TypeScript 2.1. The bundle seems to build as expected but the error message is troubling. Can anyone point out what I'm doing wrong here? Or is it a problem with rxjs\Subject.d.ts per the error (that mentioned line (Subject.d.ts:9,43) does use and innocent extends keyword)?

ts-loader: Using typescript@2.1.4 and C:Repro\stuff\tsconfig.json
Hash: f24da06626836e4fc997
Version: webpack 2.1.0-beta.28
Time: 4256ms
Asset     Size  Chunks             Chunk Names
app.js  3.01 kB       0  [emitted]  app
  [1] ./src/main.ts 372 bytes {0} [built]
    + 1 hidden modules

ERROR in C:Repro\stuff\node_modules\rxjs\Subject.d.ts
(9,43): error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.

main.ts

import { Observable } from "rxjs";

Observable.timer(3000, 5000)
  .timeInterval()
  .subscribe((interval) => console.log(interval));

package.json

{
  "name": "stuff",
  "version": "1.0.0",
  "scripts": {
    "build": "webpack"
  },
  "devDependencies": {
    "@types/core-js": "^0.9.35",
    "ts-loader": "^1.3.2",
    "typescript": "^2.1.4",
    "webpack": "^2.1.0-beta.25"
  },
  "dependencies": {
    "rxjs": "^5.0.1",
    "tslib": "^1.2.0"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "module": "commonjs",
    "importHelpers": true,
    "target": "es5",
    "noEmitHelpers": true
  }
}

webpack.config.js

module.exports = {
  name: 'server',
  target: 'node',
  entry: { 'app': './src/main.ts' },
  output: { path: './bin/', publicPath: 'bin/', filename: '[name].js' },
  externals: { rxjs: 'commonjs rxjs' },
  module: { rules: [{ test: /\.ts$/, loader: 'ts-loader' }], },
  resolve: { extensions: ['.ts'] }
};

Answer 1

Looks like this is tracked under this typescript issue which should be fixed in TypeScript 2.1.5