For anyone interested in session types, we are currently working on implementing a library for them, in Rust[0]. However, as you point out, Rusts types are affine, not linear, so we're also working on a compiler plugin for Rust that let's you track protected types and make sure they aren't dropped, letting you sort of emulate linear types[1]. Most of this is still in a pretty early state (neither actually compile at the moment), and there are some fundamental problems with the plugin (it's impossible afaik for compiler plugins to examine external crates), but someone might find it interesting. Eventually, our goal is to use these tools to solve some concurrency problems in Servo.

[0] https://github.com/Munksgaard/rust-sessions [1] https://github.com/Manishearth/humpty_dumpty