title: Incompatible peer dependencies found - upgrading Angular from 8 to 9
body: <p>I am following the official document to upgrade. </p>
  
  <p>This step completed without any errors.</p>
  
  <pre><code>ng update @angular/core@8 @angular/cli@8
  </code></pre>
  
  <p>Next step failed.</p>
  
  <pre><code>ng update @angular/core @angular/cli
  The installed Angular CLI version is older than the latest stable version.
  Installing a temporary version to perform the update.
  Installing packages for tooling via npm.
  Installed packages for tooling via npm.
  Using package manager: 'npm'
  Collecting installed dependencies...
  Found 45 dependencies.
  Fetching dependency metadata from registry...
                    Package "@angular/core" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/animations" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/compiler" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/forms" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/common" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/platform-browser" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/compiler-cli" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/router" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@angular/platform-browser-dynamic" has a missing peer dependency of "tslib" @ "^1.10.0".
                    Package "@ngtools/webpack" has an incompatible peer dependency to "typescript" (requires "&gt;=3.4 &lt; 3.6", would install "3.7.5").
  Incompatible peer dependencies found.
  Peer dependency warnings when installing dependencies means that those dependencies might not work correctly together.
  You can use the '--force' option to ignore incompatible peer dependencies and instead address these warnings later.
  
  </code></pre>
  
  <p>I checked the node_modules and the correct version of tslib is installed.
  I manually added the tslib entry and ran npm install to see if the error goes away.</p>
  
  <pre><code>  "dependencies": {
      "@angular/animations": "^8.2.14",
      "@angular/common": "^8.2.14",
      "@angular/compiler": "^8.2.14",
      "@angular/core": "^8.2.14",
      "@angular/forms": "^8.2.14",
      "@angular/language-service": "^8.2.14",
      "@angular/platform-browser": "^8.2.14",
      "@angular/platform-browser-dynamic": "^8.2.14",
      "@angular/router": "^8.2.14",
      "@ng-bootstrap/ng-bootstrap": "^5.3.0",
      "classlist.js": "^1.1.20150312",
      "core-js": "^3.6.4",
      "npm": "^6.13.7",
      "rxjs": "^6.5.4",
      "web-animations-js": "^2.3.2",
      "zone.js": "~0.9.1"
    },
    "devDependencies": {
      "@angular-devkit/architect": "^0.803.25",
      "@angular-devkit/build-angular": "^0.803.25",
      "@angular-devkit/build-optimizer": "^0.803.25",
      "@angular-devkit/build-webpack": "^0.803.25",
      "@angular-devkit/core": "^8.3.25",
      "@angular-devkit/schematics": "^8.3.25",
      "@angular/cli": "^8.3.25",
      "@angular/compiler-cli": "^8.2.14",
      "@ngtools/webpack": "^8.3.25",
      "@schematics/angular": "^8.3.25",
      "@schematics/update": "^0.803.25",
      "@types/jasmine": "^3.5.4",
      "@types/jasminewd2": "^2.0.8",
      "@types/node": "^12.12.27",
      "tslib": "^1.10.0",
      "codelyzer": "^5.2.1",
      "jasmine-core": "^3.5.0",
      "jasmine-spec-reporter": "~4.2.1",
      "karma": "^4.4.1",
      "karma-chrome-launcher": "~3.1.0",
      "karma-coverage-istanbul-reporter": "^2.1.1",
      "karma-jasmine": "~2.0.1",
      "karma-jasmine-html-reporter": "^1.5.2",
      "protractor": "^5.4.3",
      "rxjs-tslint": "^0.1.7",
      "ts-node": "^8.6.2",
      "tslint": "^5.20.1",
      "typescript": "~3.4",
      "webpack": "^4.41.6",
      "webpack-dev-server": "^3.10.3"
    }
  </code></pre>
  
  <p>ng v output</p>
  
  <pre><code>Angular CLI: 8.3.25
  Node: 12.13.0
  OS: win32 x64
  Angular: 8.2.14
  ... animations, common, compiler, compiler-cli, core, forms
  ... language-service, platform-browser, platform-browser-dynamic
  ... router
  
  Package                           Version
  -----------------------------------------------------------
  @angular-devkit/architect         0.803.24
  @angular-devkit/build-angular     0.803.25
  @angular-devkit/build-optimizer   0.803.24
  @angular-devkit/build-webpack     0.803.25
  @angular-devkit/core              8.3.24
  @angular-devkit/schematics        8.3.24
  @angular/cli                      8.3.25
  @ngtools/webpack                  8.3.24
  @schematics/angular               8.3.24
  @schematics/update                0.803.24
  rxjs                              6.5.4
  typescript                        3.4.5
  webpack                           4.41.5
  </code></pre>
  
  <p>I haven't tried to use --force option. Is there another way?</p>