Cannot redeclare block-scoped variable 'ngDevMode' : <p>My app in on Angular 5. Here is how the package.json looks like</p>

<pre><code>{
  "name": "myapp",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build --prod",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^5.2.0",
    "@angular/common": "^5.2.0",
    "@angular/compiler": "^5.2.0",
    "@angular/core": "^5.2.0",
    "@angular/forms": "^5.2.0",
    "@angular/http": "^5.2.0",
    "@angular/platform-browser": "^5.2.0",
    "@angular/platform-browser-dynamic": "^5.2.0",
    "@angular/router": "^5.2.0",
    "@types/file-saver": "0.0.1",
    "angular-2-dropdown-multiselect": "^1.6.0",
    "angular2-csv": "^0.2.5",
    "bootstrap": "^3.3.7",
    "core-js": "^2.4.1",
    "file-saver": "^1.3.3",
    "ngx-bootstrap": "^1.9.3",
    "ngx-clipboard": "^8.1.0",
    "ngx-loading": "^1.0.14",
    "ngx-pagination": "^3.0.0",
    "ngx-toastr": "^6.4.0",
    "rxjs": "^5.5.6",
    "zone.js": "^0.8.19"
  },
  "devDependencies": {
    "@angular/cli": "~1.7.0",
    "@angular/compiler-cli": "^5.2.0",
    "@angular/language-service": "^5.2.0",
    "@types/jasmine": "~2.8.3",
    "@types/jasminewd2": "~2.0.2",
    "@types/node": "~6.0.60",
    "codelyzer": "^4.0.1",
    "jasmine-core": "~2.8.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~2.0.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~4.1.0",
    "tslint": "~5.9.1",
    "typescript": "~2.5.3"
  }
}
</code></pre>

<p>Everything is fine so far. Now I need to use a datepicker in my app. So I installed angular-io-datepicker</p>

<pre><code>npm install angular-io-datepicker --save
</code></pre>

<p>Now, when I do a ng serve (after including the  OverlayModule and DatePickerModule in app.module.ts ), it gives me the below error</p>

<pre><code>ERROR in node_modules/@angular/core/src/render3/ng_dev_mode.d.ts(9,11): error TS2451: Cannot redeclare block-scoped variable 'ngDevMode'.
node_modules/angular-io-overlay/node_modules/@angular/core/src/render3/ng_dev_mode.d.ts(9,11): error TS2451: Cannot redeclare block-scoped variable 'ngDevMode'.
</code></pre>

<p>Any suggestions on what could be wrong and how to fix it? I was earlier using this module successfully with Angular 4. Then I upgraded to Angular 5 and it broke. Now even if I rollback to angular 4, this module still gives me the same problem. </p>
