Yes, there is a class RacketMenuItem in the implementation of racket/gui.

Then is there an error or warning about such name collision? The program run without any error except the init return false. Or for objc classes there isn’t a name collision error?

It looks like the libobj function objc_allocateClassPair returns NULL on collision, but define-objc-class currently just gives up silently when that happens.

on reducing barriers in the Racket community by Matthew Butterick

https://groups.google.com/d/msg/racket-users/TU5n-Z_odLY/f2KzHK7eCQAJ