Intermediary between public and private members

Post · https://lobste.rs/s/fonp7g

Say I were to have a `struct Foo { pub public: Bar, restricted: Qux }` where ‘restricted’ is some member variable which I want to be able to get, but not set, from outside of the struct methods. Normally, I would write a getter method `impl Foo { pub fn restricted(&self) -> &Qux { self.restricted }}` which isn’t very much typing, and probably I could generate these automatically with an IDE or a plugin. But all the same, why not build this into the declaration syntax with a modifier in between `private` (implicit in Rust but some languages have it) and `public`? Maybe something like `read` so that we could have `struct Foo { x, read y, pub z }` Where x is genuinely private to the struct and can only be read or written by member functions, y can be read by anyone but not modified arbitrarily, and z can be read or written to by anyone? This would need to distinguish between access and mutation of foo.y, which may not be trivial but doesn’t seem outwardly especially difficult. I’m wondering if there are hidden gotchas here that make this a lot more complex from a language design perspective, or less ergonomic than I’m assuming. If not, it seems like a straightforward feature for future languages to implement, worth an extra keyword, I would think. And if it it possible and desirable, what should the default be? It makes some sense to be that read-only is a more sensible default than full privacy if all three states are available. Eager to hear people’s thoughts.

First seen by Oriel on Oct 20, 2026, 07:39 UTC.