@cknitt Let me test with small repo project before merging. I'd like to check whether the deprecation msg seems too annoying for user.

@cknitt When I ran it on a small-scale test project, a lot of warnings appeared. Unless I disable the warnings, it seems like it would be quite annoying. Is this okay?

@mununki Sorry, I lost track of this. I think this is fine, after all we want people to migrate to JSX 4, and they can always disable deprecation warnings altogether.