Your "solution" is possible in many languages. It's just to give threads complete ownership of data they use. It doesn't require a special type system.

In general I don't think Rust actually adds much abstraction that isn't already in say Python. What it does is enforce tight constraints.

The constraints are important. They're what let you code safely, and also give the compiler the ability to optimize better.

Not sure those optimisations are worth much. And it's only safety by forcing lowest common denominator code and making you justify everything to a dumb compiler. Rust serves a niche, but it is a tight niche IMO.

Aliasing info is hugely important in optimization. In fact, it's needed to solve this very bug.

Aliasing info is, fundamentally, what allows Rust to have memory safety without GC.