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I used to think that the solution to mutable state was to prohibit it and code with immutable structures all the time, but after a few years of Rust, I think it

I used to think that the solution to mutable state was to prohibit it and code with immutable structures all the time, but after a few years of Rust, I think it's the wrong approach. The right way to handle mutable state is not to pretend it doesn't exist but to accept it as a reality of complex systems and to encode its management in the type system of the language. And that's exactly what Rust does. With Rust, I no longer feel dirty whenever I have mutable state and I trust Rust to not just keep my code bug free but also to make me think carefully about mutable state and how to design my code with it in mind.

zozbot234 5y ago
Rust prohibits shared mutable state as part of the basic language (or rather its 'safe' subset), relegating it to special-cased "interior mutability" constructs. This is essentially "as immutable as you can get" in a low-level, systems programming language. (Other languages can thread state mutations explicitly as part of a generally "immutable" design, but that doesn't give you support for the expected low-level features, so instead it's part of the language in Rust.)