Yeah. Casey is just some guy who’s good at software and YouTube. I’ve worked with dozens of people at his level technically. But very few with his interest and skill at making videos.

It’s a pity there’s not more people like him. I’ve met some incredibly smart people in the FP world. I wish more of them made approachable YouTube videos explaining what they know. I recently learned about “Safe Haskell” which, if adapted to rust and other languages, could solve a lot of the security problems with npm and cargo. But nobody knows about it! We need FP Casey.

Safe Haskell is just a worst version of Rust's unsafe. What it actually does is equivalent to Rust's #![forbid(unsafe_code)] which immediately lead to a question: so Haskell has unsafe, just like Rust? And of course it does. Any practical systems language has unsafe in one form or another, not only for FFI but also for performance, Rust is just honest about it.

There's two reasons Safe Haskell is substantially worse than what Rust does. Safe Haskell works by annotating code that is safe, but that's entirely backwards. We need to annotate unsafe code, and explain in plain English exactly why it is okay in that particular instance (of course it would be better to explain in code, like, give a formal proof that is checked by the compiler, but then it isn't unsafe anymore!). Safe Haskell answer for that is to annotate good unsafe code as trustworthy, but that doesn't work because it doesn't goes in detail on why the code is trustworthy (to do so you really need to go into the details, you can't handwave it). It's the // SAFETY comments that are at the heart of Rust's unsafe, carefully explaining safety invariants that must be kept (specially important if we are modifying code), not unsafe { } blocks.

The second reason is much simpler. It's optional, and approximately nobody uses Safe Haskell or cares about it. If people used it we would have something to improve upon. So Rust achievement here is mostly sociological, it's a community of programmers that care about safety. Which is good given that a Rust program typically have much more unsafe code than a Haskell program.

Here's a thread about Safe Haskell issues https://www.reddit.com/r/haskell/comments/zwkqke/deprecating... that links to https://discourse.haskell.org/t/deprecating-safe-haskell-or-...

And an older thread https://www.reddit.com/r/haskell/comments/msa3oq/safe_haskel...