Is this a bug report?

Yes

Can you also reproduce the problem with npm 4.x?

Yes

Which terms did you search for in User Guide?

componentDidCatch, error boundaries

Environment

1. node -v: 8.9.2

2. npm -v: 5.5.1

3. yarn --version (if you use Yarn): 0.17.10

4. npm ls react-scripts (if you haven’t ejected): 1.0.0

5. Operating system: Linux

6. Browser and version (if relevant): Chrome 63

Steps to Reproduce

1. bootstrap app with create-react-app
2. create an error boundary
3. trigger an error in a child of that error boundary

Expected Behavior

I would assume React dealt with the error, and no overlay was necessary.

Actual Behavior

The error overlay is placed on top of the app, like an uncaught error occurred. If I manually remove the
error overlay from the DOM (via devtools), the correct UI is rendered below.

Reproducible Demo

https://codesandbox.io/s/jvrwr388wv