Comment by tialaramex

Fair. Two further thoughts:

1. Rust also has other safety features that may be relevant to your interests. It is Data Race Free. If your existing safe-but-slow language offers concurrency (and it might not) it almost certainly just tells you that all bets are off if you have a Data Race, which means complicated concurrent programs exhibit mysterious hard-to-debug issues -- and that puts you off choosing concurrency unless it's a need-to-have for a project. But with Data Race Freedom this doesn't happen. Your concurrent Rust programs just have normal bugs that don't hurt your brain when you think about them, so you feel free to pick "concurrency" as a feature any time it helps.

2. The big surface area of iMessage is partly driven by Parsing Untrusted File Formats. You could decide to rewrite everything in Rust, or, more plausibly, Swift. But this is the exact problem WUFFS is intended to solve.

WUFFS is narrowly targeted at explaining safely how to parse Untrusted File Formats. It makes Rust look positively care free. You say this byte from the format is an 8-bit unsigned integer? OK. And you want to add it to this other byte that's an 8-bit unsigned integer? You need to sit down and patiently explain to WUFFS whether you understand the result should be a 16-bit unsigned integer, or whether you mean for this to wrap around modulo 256, or if you actually are promising that the sum is never greater than 255.

WUFFS isn't in the same "market" as Rust, its "Hello, world." program doesn't even print Hello, World. Because it can't. Why would parsing an Untrusted File Format ever do that? It shouldn't, so WUFFS can't. That's the philosophy iMessage or similar apps need for this problem. NSO up against WUFFS instead of whatever an intern cooked up in C last week to parse the latest "must have" format would be a very different story.