paperplane
It’s opt-in in Swift 5 mode and opt-out in Swift 6 mode, the Swift 6 compiler supports both modes though and lets you migrate a codebase on a module-by-module basis.
Agree that opt-in sort of defeats the point, but in practice it’s a sort of unavoidable compromise (and similar to unsafe Rust there will always be escape hatches)
Counterpoint, I believe the Swift syntax strikes a much better balance than Rust in terms of ergonomics and argument labels are awesome for designing fluent APIs. There are things that Rust does better, aside from having a bigger ecosystem, namely the whole borrowing/ownership system, though they’re catching up (noncopyable types and references are coming soon).
The concerns about ARC are generally a bit overstated, ARC only comes into play with classes, which modern Swift greatly deemphasizes in favor of structs, enums and protocols. Sure, sometimes you need them, especially when interoperating with Objective-C, but Rust has its escape hatches for reference counting too (Rc/RefCell, Arc/Mutex), those are just (intentionally) a bit more verbose.
In short, Swift encourages a very similar, value-oriented programming style as Rust with a modern type system (generics, associated types etc.), while offering lots of nice syntactic sugar (property wrappers, result builders etc.)