Adding useEffect in HMR causes "Expected static flag was missing"

[sebmarkbage]

Warning: Internal React error: Expected static flag was missing. Please notify the React team.

https://twitter.com/dan_abramov/status/1593609862830759936

This was also repro:ed in Next.js by @sokra:

[gaearon]

With Fast Refresh the issue is that we shouldn't be counting Hooks after return as part of the signature. I think that's a bug that we should be able to fix.

But I wonder if we should remove this warning altogether. This was attempted in #24525 but never shipped. It always shows up when you have a conditional useEffect, as noted in #24391.

There was also #24535 and then #25216 but they are not shipped either. Maybe worth prioritizing?