[staticassertion]

I think the compiler will now give you a hint that they may be from different versions. If not, next time you see it you should open up a bug in rustc.

To anyone who gets a cryptic error message - that's a bug, report it.

[eminence32]

Yup, newer compilers will give you an explicit hint about thee types from being different versions of different crates, but older compilers did not.