Right now, bitflags contains no unsafe blocks. User code can #![forbid(unsafe_code)]. But it would be nice to have #![forbid(unsafe_code)] here too, to add to the assurance that the library doesn't contain any user-facing unsafe code if the user also uses #![forbid(unsafe_code)]. Would this be reasonable for bitflags?

I think it would have to be #![cfg_attr(not(test), forbid(unsafe_code))] to allow for tests using unsafe, but same difference.