> guaranteed optimisation to a single stack frame and no allocation where possible You are literally describing stackless coroutines. And the generator state t

> guaranteed optimisation to a single stack frame and no allocation where possible You are literally describing stackless coroutines. And the generator state transform is that optimization. If you want to get this without using generators explicitly, it's still stackless coroutines just not how Rust supports stackless coroutines. There was some discussion about making it more implicit but no progress was made in the implicit direction.