title: Typescript typecheck results taking excessively long time
body: <p>I'm converting a relatively new CRA app over to Typescript. The app is relatively new, though it is setup to be a quite complex app so it has everything from react-router, react-redux, to i18n libraries and various others. </p>
  
  <p>Everytime I run 'npm run start', typescript can take anywhere between 20s to several minutes to typecheck each change, even if nothing actually changed. </p>
  
  <p>When I run 'tsc --diagnostics', I get the following info:</p>
  
  <pre><code>Files:          5677
  Lines:        118431
  Nodes:           NaN
  Identifiers:     NaN
  Symbols:      192584
  Types:         26014
  Memory used: 242096K
  I/O read:      8.44s
  I/O write:     0.00s
  Parse time:   14.28s
  Bind time:     0.92s
  Check time:    4.63s
  Emit time:     0.00s
  Total time:   19.84s
  </code></pre>
  
  <p>I'm wondering why Nodes and Identifiers are showing as <code>NaN</code>. I haven't been able to find anyone else having this issue when they run <code>-diagnostics</code>.</p>
  
  <p>Can anyone offer any insight into this? I'm wondering if Typescript is hitting some snags compiling which is resulting in the slow typechecking.</p>
  
  <p>I'm using Typescript v3.4.1 and VS Code v1.3.3 on MacOS High Sierra. I've tried deleting/install my node_modules folder to no avail, and tried adding the <code>--incremental</code> flag which is supposed to make Typescript cache buildinfo for future compilations to go faster, but that hasn't done anything either.</p>
  
  <p>my package.json dependencies and devDependencies</p>
  
  <p>dependencies:</p>
  
  <pre><code>    "axios": "^0.18.0",
      "browser-locale": "^1.0.3",
      "date-fns": "^1.30.1",
      "i18next": "^15.0.9",
      "i18next-browser-languagedetector": "^3.0.1",
      "prop-types": "^15.6.2",
      "react": "^16.8.4",
      "react-app-polyfill": "^0.2.2",
      "react-dom": "^16.8.4",
      "react-i18next": "^10.6.2",
      "react-loadable": "^5.5.0",
      "react-redux": "^7.0.0-beta.0",
      "react-router": "^5.0.0",
      "react-router-dom": "^5.0.0",
      "react-scripts": "2.1.8",
      "react-transition-group": "^2.5.3",
      "redux": "^4.0.1",
      "redux-thunk": "^2.3.0",
      "source-map-explorer": "^1.6.0",
      "styled-components": "^4.2.0",
      "typeface-roboto": "^0.0.54",
      "typescript": "^3.4.1",
      "use-redux": "^2.2.0"
  </code></pre>
  
  <p>devDependencies</p>
  
  <pre><code>
      "@types/material-ui": "^0.21.6",
      "@material-ui/core": "^3.8.2",
      "@material-ui/icons": "^3.0.2",
      "@types/axios": "^0.14.0",
      "@types/date-fns": "^2.6.0",
      "@types/jest": "^24.0.11",
      "@types/node": "^11.13.0",
      "@types/react": "^16.8.12",
      "@types/react-dom": "^16.8.3",
      "@types/react-loadable": "^5.5.1",
      "@types/react-redux": "^7.0.6",
      "@types/react-router": "^4.4.5",
      "@types/redux": "^3.6.0",
      "@types/redux-thunk": "^2.1.0",
      "@types/styled-components": "^4.1.12",
      "@types/react-router-dom": "^4.3.1",
      "enzyme": "^3.8.0",
      "enzyme-adapter-react-16": "^1.8.0",
      "jest": "^23.6.0",
      "jest-dom": "^3.0.1",
      "prettier": "1.15.3",
      "react-axe": "^3.1.0",
      "react-testing-library": "^5.4.4",
      "redux-devtools-extension": "^2.13.7",
      "redux-mock-store": "^1.5.3"
  </code></pre>