I'm not a Swift user, but I can tell you from C++ experience that this logic doesn't mitigate a complex programming language.

* If you're in a team (or reading code in a third-party repo) then you need to know whatever features are used in that code, even if they're not in "your" subset of the language.

* Different codebases using different subsets of the language can feel quite different, which is annoying even if you know all the features used in them.

* Even if you're writing code entirely on your own, you still end up needing to learn about more language features than you need to for your code in order that you can make an informed decision about what goes in "your" subset.

I would remove result builders and all other uses of @attributes that change the semantics of the code (e.g property wrappers).

I would remove the distinction between value types and reference types at the type level. This has caused so many bugs in my code. This distinction should be made where the types are used not where they are defined.

I would remove everything related to concurrency from the language itself. The idea to let code execute on random threads without any explicit hint at the call site is ridiculous. It's far too complicated and error prone, which is why Swift designers had to radically change the defaults between Swift 6.0 and 6.2 and it's still a mess.

I would remove properties that are really functions (and of course property wrappers). I want to see at the call site whether I'm calling a function or accessing a variable.

I would probably remove async/await as well, but this is a broader debate beyond Swift.

And yes you absolutely do have to know and use all features that a language has, especially if it's a corporate language where features are introduced in order to support platform APIs.

But you have to know all of them to read other people's code.

To answer your question: I would immediately get rid of guard.

Also, I think the complexity and interplay of structs, classes, enums, protocols and now actors is staggering.

i would get rid of associatedtype, borrowing, consuming, deinit, extension, fileprivate, init, inout, internal, nonisolated, open, operator, precedencegroup, protocol, rethrows, subscript, typealias, #available, #colorLiteral, #else, #elseif, #endif, #fileLiteral, #if, #imageLiteral, #keyPath, #selector, #sourceLocation, #unavailable, associativity, convenience, didSet, dynamic, indirect, infix, lazy, left, mutating, nonmutating, postfix, precedence, prefix, right, unowned, weak, and willSet

You can take this approach in personal projects - with teams you need to decide on this and then on-board people into your use of the language. This does not work.

1. You don't have to use it all, but someone will. And there are over 200 keywords in the language: https://x.com/jacobtechtavern/status/1841251621004538183

2. On top of that many of the features in the language exist not because they were carefully designed, but because they were rushed: https://news.ycombinator.com/item?id=47529006