> The only time I hear about a mainstream language being immutable by default is from Rust people telling me that Rust is a mainstream language now. Most mains

> The only time I hear about a mainstream language being immutable by default is from Rust people telling me that Rust is a mainstream language now. Most mainstream languages are old, they can't be immutable my default without breaking backwards compatibility. I'm talking about the design direction of languages that are already based on mutability. For example, Java added Records which are immutable, as well as overhauling the date/time api with an immutable version. > This doesn't make such a thing desirable for other languages. I've used this pattern in other languages, none of this is a silver bullet that makes software engineering easy; but I do find it makes some code much easier to test and reuse.