I assume you're referring to typestate. One of the reasons that typestate was removed is that practically everything you can do with typestate can be done with session types instead. Constraints can be modeled as unique types with a trusted transition function from state to state. The unique type system used for memory management in Rust nicely doubles as a session type system. This is actually done today with the pipes compiler—it uses unique types to statically ensure that you can't violate a communications protocol, just as typestate can.

One of our focuses for 1.0 is on aggressively pruning features that overlap, to reduce language complexity and to avoid committing ourselves to language features we might not need. However, future versions of the language might add more static analyses as they prove useful.