[chlorion]

I agree that "four times slower" may not apply in Rust specifically.

I do think the idea that exceptions are faster at runtime (at least in micro benchmarks) can be ported across languages though just due to the way exceptions are implemented. In any language, a caller of a function that can return a Result or Option always need to branch to unwrap the returned value, but callers of functions that can throw don't have these branches at all (on platforms with "zero cost" exceptions). Whether or not it actually matters in practice is certainly debatable. I would guess that it will never be a real problem for most people.

Wrt to std::optional and std::expected, I also have found them to be pretty clunky and limited, especially compared to the Rust counterparts! The lack of pattern matching is one issue, the lack of optional references is another, and they just don't integrate with the language as well since most libraries and even std functions don't use them!