Maybe we need to introduce the term "value safety" to complement "type safety".

If a language is merely type-safe, then it might be OK to silently replace a value with a different one of the same type, sure, fine. Who cares if the program transmits the wrong message to the wrong recipient as long as it's definitely some message and some recipient?

But a value-safe language, I suggest, is one that doesn't pull this kind of switcheroo.