[Compiler Bug]: TypeError: isUndefined is not a function (it is undefined)

[Robert27]

What kind of issue is this?

• React Compiler core (the JS output is incorrect, or your app works incorrectly after optimization)
• babel-plugin-react-compiler (build issue installing or using the Babel plugin)
• eslint-plugin-react-compiler (build issue installing or using the eslint plugin)
• react-compiler-healthcheck (build issue installing or using the healthcheck script)

Link to repro

https://github.com/Robert27/react-compiler-repro

Repro steps

This bug happens in my Expo app and only with the calendar lib.
The repro repo uses the react compiler version expo recommends, but it also happens with React 19.1 with the latest React compiler alpha version.

1. Navigate to Calendar tab.
2. Error: TypeError: isUndefined is not a function (it is undefined)

The only workaround is to completely disable the compiler. Using 'use no memo' or disabling the file in the babel config does not work.

How often does this bug happen?

Every time

What version of React are you using?

19.0

What version of React Compiler are you using?

19.0.0-beta-af1b7da-20250417