This is all well and dandy for some usage scenarios but breaks in others, eg. scene graphs and GUI's.
A scene graph needs 2 mutable references, and has nothing to do with ownership. Same issue exists with GUI's. The pattern that Rust forces is to always request a reference, which incurs a performance penalty while retrieving the same reference again and again and again.
I am not familiar with scene graphs, but what is the problem with borrowing or refcounting? This article showed how you can have multiple mutable references in Rust, even multiple mutable references running in parallel threads.
Rust is becoming less special in this area. Languages such as Dlang, Vlang, and Julia have added optional ownership and borrowing. As these offerings are optional, many can see this as greater programmer freedom to decide what to use for their projects, with languages that are easier to use or read.
> Rust is becoming less special in this area. Languages such as Dlang, Vlang, and Julia have added optional ownership and borrowing
Isn't the crux that Rust does those things without a garbage collector, that's the novel part? Someone correct me if I'm wrong (likely), but I think all those languages have garbage collectors, which Rust doesn't.
Yes, it's a critical distinction that's important in many systems domains, but getting some form of ownership policy and method - even if implemented with a GC I think is a step forward in terms of building reliable code.
The thing about it being optional in some languages is that it's an experiment, but one that as a feature it really pays off the more code in the ecosystem is compliant to ownership tracking. For rust, it's the vast majority of it (with opt out explicitly findable..) For languages offering it optionally, it's harder to assemble the full benefit.
I guarantee they'll be complaining about unsafe rust in 10-15 years, mark my words. Just like they said exceptions "force" a programmer to deal with all error cases (newsflash, they still ignore it), rust will not eliminate memory errors.
I miss the clear distinction between exclusive access and shared access when I work in GC languages. Knowing clearly when you are allowed/expected to modify a value, and when you are expected to only read the value ends up being very useful and it has poisoned my brain when working in Python/JS/Go where some values are internally pointers and there's no standard to learn once for when a mutation is safe or if you should always make a copy
One way to deal with this in GC languages is to have a separate read-only view on a mutable object. The example that comes to mind, though it's a bit more complex than a view on a simple data structure is CancellationToken (read only) vs CancellationTokenSource (writable in the sense of having "cancel()" method) in C#. I'm not saying it's better than proper mutability support but it does work well enough sometimes.
A scene graph needs 2 mutable references, and has nothing to do with ownership. Same issue exists with GUI's. The pattern that Rust forces is to always request a reference, which incurs a performance penalty while retrieving the same reference again and again and again.
Isn't the crux that Rust does those things without a garbage collector, that's the novel part? Someone correct me if I'm wrong (likely), but I think all those languages have garbage collectors, which Rust doesn't.
The thing about it being optional in some languages is that it's an experiment, but one that as a feature it really pays off the more code in the ecosystem is compliant to ownership tracking. For rust, it's the vast majority of it (with opt out explicitly findable..) For languages offering it optionally, it's harder to assemble the full benefit.