Iterators do indeed not force the removal of bounds check, but that's simply because they don't exist to remove in the first place. That's because iterators act

Iterators do indeed not force the removal of bounds check, but that's simply because they don't exist to remove in the first place. That's because iterators actually do use `unsafe` internally. They are a safe abstraction. // This is unidiomatic. Don't do this. for i in 0..100 { // Oops! Array indexing. Here's a nasty bounds check! array[i] * 2 } // Very unidiomatic. Never do this! Not even as an // optimization. You should properly use safe abstractions // in stead. for i in 1..100 { // Oh, NOOOO! This isn't supposed to be C! unsafe { array.get_unchecked(i) * 2 } } // This is still unidiomatic unless you want to use // it to explicitly show your code has side-effects. // However, we're completely rid of the bounds check and // yet it's perfectly safe perfectly safe. // The only way this could be unsafe is if rustbelt's // formal proofs, reviews, audits // and (probably) MLOC of thoroughly tested and // possibly fuzzed code using this in practice // have all somehow missed an unsoundness bug // in one of the more used safe abstractions in the // core library for years. for a in array { // Look, Ma! No indexing, therefore no bounds check! // Internally `get_unchecked` is (conceptually) used // but it's perfectly safe! a * 2 } // This is idiomatic Rust. Again, there's no bounds check // to start with, since the save abstraction knows // exactly how many elements are in the array and // that the borrow checker will ensure nobody can // possibly invalidate its indexing. // Ditto what was said above that the safe abstraction // is pretty much guaranteed to be sound. a.iter().map(|a| a * 2).collect()