To wit, the Rust compiler is "sufficiently smart" in an extremely high number of scenarios such that it can achieve optimal performance by eliding things like b

To wit, the Rust compiler is "sufficiently smart" in an extremely high number of scenarios such that it can achieve optimal performance by eliding things like bounds checks when it's able to determine that they would never fail. This is, in my experience, the overwhelming majority of idiomatic Rust code. For cases where it can't, and performance is absolutely critical, there are easy escape hatches that let you explicitly elide the checks yourself.