One of the genius things about Swift is its interop with Objective C. Made the switch over considerably easier for developers. I’m not sure what that looks like in a Rust world.
Rust is also just a more complex language. I’m not convinced the benefits would have been worth it.
Not just interoperability with Objective C but with C (full) and C++ (increasingly better but not full) as well.
Swift is also interoperable with different versions of itself courtesy of the Swift stable ABI (Application Binary Interface)[0], which they invested a significant amount of time into at the expense of adding other new features to the language, which have come along later.
Rust offers a different approach: recompile everything and static linking.
These days I mainly write Rust but I did write a semi complex iOS app and enjoyed Swift. I just didn't love how slow the type checker was and how it got lost. I recall having to break things into smaller bits to help the compiler, and there were some oddities about the language.
The gap between the two languages is quite small, it just makes me wish Apple was also all-in on Rust
In the last year they’ve added improvements to the type checker to speed it up, those would have been released now.
They have further and much more significant changes that I think might have recently landed in the development version. That should make an even bigger difference. But it’s not in a released version yet.
And yes, none of us like that one part of Swift. Especially the DRASTIC difference compared to objective-C which really only checked syntax and little else.
It’s still probably my favorite language right now though I don’t get to write in it much.
There’s no reason to invent your own head canon, the influence was openly acknowledged when Swift was new and it continues now that the language is developed out in the open (see Swift Ownership Manifesto)
I believe Swift tends to use reference counting and copy-on-write strategies. This, like GC, is less for the programmer to think about and doesn't require the semantic checks, but sometimes the performance cost is unacceptable compared to what you'd write in Rust.
You can choose to use either refcounting or unique ownership for your types. For most use cases, refcounted (+ copy-on-write) is the best choice and is the default, but the truetype interpreter made extensive use of non-refcounted types to achieve this performance.
They have either recently added or talked about a borrow style system in the language as a way to avoid more copies and speed things up/lower memory usage/help with asynchronous programming.
Swift takes the right approach in language ergonomics, many of its use cases would be much harder with explicit .clone() all over the place, lack of back references, no standard ABI for binary libraries, interop with Objective-C and C++, no standard concurrency runtime, or error handling types.
Rust 2026 roadmap has language ergonomics on it for a reason.
That said, outside Apple ecosystem you probably better with Rust, or if one has no GC issues, OCaml, Haskell, F#, Scala, C#.
Apple has a runtime system that looks a lot like smalltalk. Everything at that layer is dynamic. They needed a language that could seamlessly interact with that system.
https://faultlore.com/blah/swift-abi/ (written by a core Rust developer)
[1] apart from the basic/universal C one, which prevents exposing any useful Rust semantics over the interface