Given
```js
function ThrowInEffect() {
  React.useEffect(() => {
    throw new Error('passive effect')
  }, [])
  return null;
}
```

In React 17 this error got logged to the console (and triggered the error overlay in create-react-app) regardless of whether `ThrowInEffect` was a child of an Error Boundary or not.

In React 18 (`createRoot` and legacy root API) an Error Boundary will prevent logging that error to the console (and not trigger the error overlay in create-react-app).

Errors during render work like they did in React 17.

Behavior in React 17: https://codesandbox.io/s/react-17-error-boundaries-vp21e?file=/src/index.js
Behavior in React 18: https://codesandbox.io/s/react-18-error-boundaries-psd56?file=/src/index.js


Recording of effect errors in React 17 and 18 and with and without Error Boundaries_

https://user-images.githubusercontent.com/12292047/122749780-053ced00-d28e-11eb-98ce-075dcdc53ee2.mp4


if (destroy === null) {
              addendum =
                ' You returned null. If your effect does not require clean ' +
                'up, return undefined (or nothing).';
            } else if (typeof destroy.then === 'function') {
              addendum =
                '\n\nIt looks like you wrote useEffect(async () => ...) or returned a Promise. ' +
                'Instead, write the async function inside your effect ' +
                'and call it immediately:\n\n' +
                'useEffect(() => {\n' +
                '  async function fetchData() {\n' +
                '     You can await here\n' +
                '    const response = await MyAPI.getData(someId);\n' +
                '     ...\n' +
                '  }\n' +
                '  fetchData();\n' +
                `}, [someId]);  Or [] if effect doesn't need props or state\n\n` +
                'Learn more about data fetching with Hooks: https:reactjs.org/link/hooks-data-fetching';
            } else {
              addendum = ' You returned: ' + destroy;
            }
            console.error(
              'An effect function must not return anything besides a function, ' +
                'which is used for clean-up.%s',
              addendum,
            );
          }
        }