'React' was used before it was defined

If you are only getting this error for .js files, make sure @typescript-eslint/parser is being used exclusively on Typescript files.

.eslintrc.json (abbreviated)

{
  "overrides": [
    {
      "files": ["**/*.ts", "**/*.tsx"],
      "plugins": ["@typescript-eslint"],
      "rules": {
        "no-use-before-define": "off",
        "@typescript-eslint/no-use-before-define": ["error"],
      },
    }
  ],
  // WRONG: Do not use @typescript-eslint/parser on JS files
  // "parser": "@typescript-eslint/parser",
  "plugins": [
    "react",
    // "@typescript-eslint"
  ],
}

That is how I resolved my problem.

1. First of all, go to the node_modules/react-scripts/config/webpack.config.js and change cache to false, because this will help you to understand what works and what is not then you changing eslint file. I found it here

 cache: true, // You can set it to false
 formatter: require.resolve('react-dev-utils/eslintFormatter'),

2. Add ENV varialbe to .env file. More info

 EXTEND_ESLINT=true

3. From now CRA will have to use your local eslint for linting during your build and we have control to disable some rules, in my case in .eslintrc:

rules: {
    "@typescript-eslint/no-use-before-define": "off"
},

From the official documentation.

"rules": {
  // note you must disable the base rule as it can report incorrect errors
  "no-use-before-define": "off",
  "@typescript-eslint/no-use-before-define": ["error"]
}

The bug occurs due to mismatch of @typescript-eslint versions in react-scripts and your local package.json - GitHub issue

You can downgrade the packages until react-scripts updates their version.

    "@typescript-eslint/eslint-plugin": "4.0.1",
    "@typescript-eslint/parser": "4.0.1",

EDIT 2020-09-14

It seems the bug is not related to react-scripts version of @typescript-eslint since multiple people reported the same bug without using react-scripts.

Anyway, the workaround remains the same - downgrade to the working version of @typescript-eslint until the fix is available.

EDIT 2020-10-24

[email protected] has been published with updated @typescript-eslint. Using the newest version should solve the issue.

EDIT 2020-11-04

If after upgrading the packages the error is still there, most probably your eslint config uses the wrong rule. Check out Igor's answer to fix it.