Comment by AIPedant

Hmm my read is this is a slight overstatement - Rust was always built with the idea of expressions as first class citizens, but practicality and performance requires expression-breaking keywords like “return” which don’t fit neatly in an ML-ish language and have a few plain old hacks associated with implementing them (not “hack” as in lacking robustness; I mean theoretically/formally inelegant). Likewise there’s some stuff (u8) which is a simple syntax quirk. But a lot of these return/etc oddities are because Rust is ultimately an imperative language with strong influence from functional programming.