Curious the direction of Webkit as there was a nebulous mention of select portions being rewritten from C++ to Swift. And yet, the new ECMAScript module (ESM) loader for Safari 27 is implemented in C++ (https://webkit.org/blog/17967/news-from-wwdc26-webkit-in-saf...).
Russinovitch (Azure's CTO/CISO) gave a speech at RustConf 2025 and mentions it(DirectWriteCore) took 2 engineers 6 months resulting in 154K LOC and 5-15 percent performance increase for font shaping. https://www.youtube.com/watch?v=uDtMuS7BExE&list=PL2b0df3jKK...
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
I'm surprised the code has visible LLM smells. Though, I shouldn't be surprised. I hope the important bits are still human-controlled (and the same for Apple's many operating systems that absolutely deserve to remain stable and understood).
It would be interesting to see their internal guidance on LLM use. It’s a massive amount of new power that has to be wielded carefully. That kind of guidance might mean the survival or downfall of some big corps in the next few years.
I think these are the types of things Apple should've focused on instead of half-heartedly barging ahead with SwiftUI and breaking the language in the process
No mention of AI? Hand written code?
During the State of Platform keynote, on the subject of Swift adoption across macOS, several examples were given, not only TrueType engine.
RIS is happening across all OS levels, if the keynote is to be believed.
Curious the direction of Webkit as there was a nebulous mention of select portions being rewritten from C++ to Swift. And yet, the new ECMAScript module (ESM) loader for Safari 27 is implemented in C++ (https://webkit.org/blog/17967/news-from-wwdc26-webkit-in-saf...).
No idea, maybe the private parts of the code, Safari isn't open source, or is coming later.
In any case I would have liked to have more info during the deep dive sessions.
As it is, Meet with Apple on security (a 5h long event) had much more information.
Interesting that this is published under the MIT, rather than Apple’s more favorite Apache 2, license
Why is it interesting?
Presumably because MIT is even more permissive and it’s a change in Apple’s behavior.
Back in 2023 there was talks about Microsoft rewriting the font stuff in Rust for similar reasons Apple is now doing the Swift move.
I'm not sure what became of it and if it ever shipped. If anyone knows I'd be curious.
Russinovitch (Azure's CTO/CISO) gave a speech at RustConf 2025 and mentions it(DirectWriteCore) took 2 engineers 6 months resulting in 154K LOC and 5-15 percent performance increase for font shaping. https://www.youtube.com/watch?v=uDtMuS7BExE&list=PL2b0df3jKK...
As much as I enjoyed Swift, one can only wonder what the world would look like if they had gone with Rust as their default language instead.
Modern Swift borrows a lot from Rust! And it also has its own benefits, both ergonomic and also supporting eg generic in dynamic libraries
Swift and Rust were developed at similar times. I think of them more as having similar influences than borrowing from each other.
Similar times and the Rust originator went on to work on Swift after it.
Graydon Hoare's impact on the language is marginal than that of Chris Lattner, the originator (also, Hoare joined the team much later)
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
Does it borrow borrow checker?
Welcome to the club of doing high performance text in a memory safe language!
The author discussed this a bit on Mastodon as well:
https://xoxo.zone/@numist/116716469017975106
I'm also here :)
I'm surprised the code has visible LLM smells. Though, I shouldn't be surprised. I hope the important bits are still human-controlled (and the same for Apple's many operating systems that absolutely deserve to remain stable and understood).
I assure you, every inch of the interpreter code has been stared at by humans, a lot. TBH even the assembly generated by it has.
From what I got Apple is using claude code A LOT internally
It would be interesting to see their internal guidance on LLM use. It’s a massive amount of new power that has to be wielded carefully. That kind of guidance might mean the survival or downfall of some big corps in the next few years.
Yes they are using Claude Code - not the Xcode agents.
It worries me. I hope Codex adoption picks up there.
I think these are the types of things Apple should've focused on instead of half-heartedly barging ahead with SwiftUI and breaking the language in the process
I mean they’re doing both