The TypeScript++ example looks like the type of code that JITs typically like. Python has Numba, where users affix a @jit annotation to functions to request that. It works pretty well in my experience.

However, at this point, I'm mostly of the opinion that langs need some notion of mechanical sympathy if they want to be used for high-performance. JS engines probably have tens of millions of dollars of dev effort poured into them by now, yet they get soundly beaten by WASM, which is much younger. The conceptual foundation matters a lot.

That said, there's probably a nice space for an ergonomic, reasonably fast PL that sits between Rust and JS.