and also for like $INSERT_LANG_NAME they some times do formal verification or compiler formal verification, so that's how they can be sure that language is type safe. so it's up to you to ensure if your lang or $interpreted_dynamic_lang_of_your_interest is formally verified. There is CompCert & similiar. I've heard some parts of ML/Rust been formally verified, that's their selling feature and +1 reason behind their marketing.
If you care about type safety your probably want your lang compiler/interpreter to be formally verified, but you can't do that without dipping your toes in to fundamentals of math of type theory. In theory you can do formal verification in ML/Coq etc.
and if you want your lang to be secure, there are ISO standarts secure verifications.