Error with 5.1.0-beta and React < 16.6

Describe the bug When using React < 16.6, storybook 5.1.0-beta fails to load in the browser with the following error in the dev console:

Uncaught TypeError: React.memo is not a function
    at Object../node_modules/react-inspector/dist/cjs/react-inspector.js (vendors~main.346d12fabfecf4be4f79.bundle.js:115806)
    at __webpack_require__ (runtime~main.346d12fabfecf4be4f79.bundle.js:782)
    at fn (runtime~main.346d12fabfecf4be4f79.bundle.js:150)
    at Object../node_modules/@storybook/theming/dist/convert.js (vendors~main.346d12fabfecf4be4f79.bundle.js:46334)
    at __webpack_require__ (runtime~main.346d12fabfecf4be4f79.bundle.js:782)
    at fn (runtime~main.346d12fabfecf4be4f79.bundle.js:150)
    at Object../node_modules/@storybook/theming/dist/index.js (vendors~main.346d12fabfecf4be4f79.bundle.js:46851)
    at __webpack_require__ (runtime~main.346d12fabfecf4be4f79.bundle.js:782)
    at fn (runtime~main.346d12fabfecf4be4f79.bundle.js:150)
    at Module../.storybook/theme.js (main.346d12fabfecf4be4f79.bundle.js:734)

I am upgrading from storybook 5.1.0-alpha.37

The React peerDependencies seem to suggest that any version is supported ("react": "*"), but it looks like usage of React.memo has recently made it into the codebase. Does this mean you no longer support React < 16.6? Apologies if this has been called out somewhere, but I couldn’t find it in the migration guide or changelog.

[shilman]

Gadzooks!! I just released https://github.com/storybooks/storybook/releases/tag/v5.1.0-rc.0 containing PR #6818 that references this issue. Upgrade today to try it out!

Because it’s a pre-release you can find it on the @next NPM tag.

Closing this issue. Please re-open if you think there’s still more to do.

[kaelig]

I encountered the same issue (workaround: downgrade to 5.1.0-alpha.39).