> The mental model of & being immutable and &mut being mutable, that’s what falls apart. Here are types that are taking &, and yet are mutating themselves.
&mut still implies mutability, and even the constructs like Mutex or RefCell still expose their mutability support via &mut references. Only atomics don't (they don't provide any &mut access). Note that you don't add const like in C/C++, you add &mut.
As for the VDOM caching thing, you have a point. But even if Rust had &uniq and &shared pointers, the challenge would be the same. Users might still use constructs like RefCell.
Mutex::lock() takes &self. RefCell::borrow_mut() takes &self. Those (and try_ variants) are the main ways people will use those types to gain access to their interior mutability.
Sure, both do have get_mut() which takes &mut self (though these came after 1.0), but that’s seldom how you’ll actually access it.
> But even if Rust had &uniq and &shared pointers, the challenge would be the same.
Remember again that the mutpocalypse wasn’t ever about changing the semantics, just about fixing incorrect labelling. I’m not saying the challenges would be different, just that &mut is false advertising, giving people the impression that & means an immutable reference, when it just doesn’t. &/&mut misleads people into thinking they can have immutable data structures, but you’d actually need an OIBIT (like Send) to achieve that.
> Mutex::lock() takes &self. RefCell::borrow_mut() takes &self. Those (and try_ variants) are the main ways people will use those types to gain access to their interior mutability.
Yeah they take &self, but that wasn't my point. My point was what they expose, which is MutexGuard in the case of Mutex, and if you want to modify the interior, you'll likely use the DerefMut impl which returns a &mut T. Same goes for RefCell::borrow_mut().
My point was that you don't mutate a &self reference directly in these instances, but turn a &self reference into a &mut self reference and then mutate. Again, atomics are an exception.
> just that &mut is false advertising
it is not false advertising, it implies mutable access. Had Rust been mut by default and had &T been &const T instead, I would agree with the false advertisement point. But thankfully it's non-mut by default.
Anyways, even if &mut were false advertising, and it were a bump in the learning curve, note that &uniq is such a bump too, because you have no idea what it says or implies initially. &mut makes it clear that if you want to mutate, you'll likely need a &mut somewher. But &uniq does not make this obvious, so you are required to learn something early on in Rust's comprehension, while &mut requires you to learn something later on. Generally, Rust has been criticized for having a steep learning curve at the start. In general I think it's worth it to learn Rust, but this wouldn't make it any better but worse.
RefCell allows you to get a mutable reference via an allegedly-immutable reference. That it goes via a guard type is quite immaterial. It breaks the model.
&mut implies & is immutable.
Rust is teaching an incorrect mental model, which I believe is the wrong mental model to teach. Sure, &uniq is not devoid of problems, because most of the time &mut will suggest the right thing for beginners. But the spelling &mut is categorically wrong at the fundamental technical level. It was never actually about mutability.
&mut still implies mutability, and even the constructs like Mutex or RefCell still expose their mutability support via &mut references. Only atomics don't (they don't provide any &mut access). Note that you don't add const like in C/C++, you add &mut.
As for the VDOM caching thing, you have a point. But even if Rust had &uniq and &shared pointers, the challenge would be the same. Users might still use constructs like RefCell.