Breaking: Remove support for Flow

Currently swc doesn't support Flow they are considering it, if they do we can revert this commit swc-project/swc#256

Author: Morten N.O. Henriksen

README.md

@@ -148,7 +148,7 @@ Please refer to the [User Guide](https://facebook.github.io/create-react-app/doc
 
 Your environment will have everything you need to build a modern single-page React app:
 
-- React, JSX, ES6, TypeScript and Flow syntax support.
+- React, JSX, ES6 and TypeScript syntax support.
 - Language extras beyond ES6 like the object spread operator.
 - Autoprefixed CSS, so you don’t need `-webkit-` or other prefixes.
 - A fast interactive unit test runner with built-in support for coverage reporting.

docusaurus/docs/adding-a-sass-stylesheet.md

@@ -44,18 +44,6 @@ To use imports relative to a path you specify, you can add a [`.env` file](https
 
 > **Tip:** You can opt into using this feature with [CSS modules](adding-a-css-modules-stylesheet.md) too!
 
-> **Note:** If you're using Flow, override the [module.file_ext](https://flow.org/en/docs/config/options/#toc-module-file-ext-string) setting in your `.flowconfig` so it'll recognize `.sass` or `.scss` files. You will also need to include the `module.file_ext` default settings for `.js`, `.jsx`, `.mjs` and `.json` files.
->
-> ```
-> [options]
-> module.file_ext=.js
-> module.file_ext=.jsx
-> module.file_ext=.mjs
-> module.file_ext=.json
-> module.file_ext=.sass
-> module.file_ext=.scss
-> ```
-
 > **Note:** LibSass and the packages built on top of it, including Node Sass, are [deprecated](https://sass-lang.com/blog/libsass-is-deprecated).
 > If you're a user of Node Sass, you can migrate to Dart Sass by replacing `node-sass` in your `package.json` file with `sass` or by running the following commands:
 >

docusaurus/docs/adding-flow.md

@@ -87,7 +87,7 @@ Next, create `src/setupProxy.js` and place the following contents in it:
 ```js
 const { createProxyMiddleware } = require('http-proxy-middleware');
 
-module.exports = function(app) {
+module.exports = function (app) {
   // ...
 };
 ```
@@ -97,7 +97,7 @@ You can now register proxies as you wish! Here's an example using the above `htt
 ```js
 const { createProxyMiddleware } = require('http-proxy-middleware');
 
-module.exports = function(app) {
+module.exports = function (app) {
   app.use(
     '/api',
     createProxyMiddleware({
@@ -110,6 +110,6 @@ module.exports = function(app) {
 
 > **Note:** You do not need to import this file anywhere. It is automatically registered when you start the development server.
 
-> **Note:** This file only supports Node's JavaScript syntax. Be sure to only use supported language features (i.e. no support for Flow, ES Modules, etc).
+> **Note:** This file only supports Node's JavaScript syntax. Be sure to only use supported language features (i.e. no support for ES Modules, etc).
 
 > **Note:** Passing the path to the proxy function allows you to use globbing and/or pattern matching on the path, which is more flexible than the express route matching.

docusaurus/docs/proxying-api-requests-in-development.md

@@ -17,7 +17,7 @@ This project supports a superset of the latest JavaScript standard. In addition
 - [Object Rest/Spread Properties](https://github.com/tc39/proposal-object-rest-spread) (ES2018).
 - [Dynamic import()](https://github.com/tc39/proposal-dynamic-import) (stage 4 proposal)
 - [Class Fields and Static Properties](https://github.com/tc39/proposal-class-public-fields) (part of stage 3 proposal).
-- [JSX](https://facebook.github.io/react/docs/introducing-jsx.html), [Flow](./adding-flow) and [TypeScript](./adding-typescript).
+- [JSX](https://facebook.github.io/react/docs/introducing-jsx.html) and [TypeScript](./adding-typescript).
 
 Learn more about [different proposal stages](https://tc39.github.io/process-document/).
 

docusaurus/docs/supported-browsers-features.md

@@ -30,7 +30,6 @@
       "importing-a-component",
       "using-global-variables",
       "adding-bootstrap",
-      "adding-flow",
       "adding-typescript",
       "adding-relay",
       "adding-a-router",

docusaurus/website/sidebars.json

@@ -371,7 +371,7 @@ module.exports = function (webpackEnv) {
               },
             },
             // Process application JS with swc.
-            // The preset includes JSX, Flow, TypeScript, and some ESnext features.
+            // The preset includes JSX, TypeScript, and some ESnext features.
             {
               test: /\.(js|mjs|jsx)$/,
               include: paths.appSrc,

packages/react-scripts/config/webpack.config.js

@@ -17,16 +17,6 @@ async function load() {
   ];
 }
 
-/* eslint-disable */
-// Regression test for https://github.com/facebook/create-react-app/issues/3055
-const x = async (
-  /* prettier-ignore */
-  y: void
-) => {
-  const z = await y;
-};
-/* eslint-enable */
-
 export default class AsyncAwait extends Component {
   static propTypes = {
     onReady: PropTypes.func.isRequired,