korrents

korrents · The Pragmatic Engineer Podcast

Why Rust is different, with Alice Ryhl

Alice Ryhl · 1h 05m · youtube.com ↗

23 korrents from this recording

1h
Alice Ryhl did not write this page.

Every claim below is a statement made in this recording, quoted word for word and linked to the second it was said, so you can hear it rather than take our word for it. The wording comes from the transcript published alongside the recording; the sentence above each quote is our reading of the claim, not their wording.

  1. 0:05:24 · watch on youtube.com↗

    Our reading

    Rust's defining experience is that once the code compiles it works — not literally true, but true often enough that people keep saying it.

    Their wordsI think part of what I liked about Rust is this feeling that as you write the code when it compiles it works. I mean this has to be in quotes right because obviously it's possible that there are bugs but this is something a lot of people say about Rust and there's a reason people say it even though it's not necessarily literally true.
    Interesting

  3. 0:05:48 · watch on youtube.com↗

    Our reading

    A language can only give you the feeling that compiling means working if it has a type system — that is where it all starts.

    Their wordsI think to have a language that feels this way you have to have a type system. That's where it all starts.
    Interesting
  4. 2 min later

  5. 0:08:06 · watch on youtube.com↗

    Our reading

    For a TypeScript team, Rust belongs on the backend — API servers — and not in the front end.

    Their wordsBut okay, so to begin with, I think when it comes to TypeScript, Rust fits in as the backend language. That's where I would put it. I wouldn't use it in the front end. I think it's a pretty good fit for backends, API servers.
    Interesting
  6. 2 min later

  7. 0:10:12 · watch on youtube.com↗

    Our reading

    Examples in documentation should be compiled and run as tests, so that changing the code breaks the docs instead of quietly outdating them.

    Their wordsNow the thing is you can of course write examples in your documentation and Rust makes all examples into tests. This means that if you change the underlying code now your test fails. And so this means that you can't even you can't forget to update your examples in your documentation.
    Interesting
  8. 2 min later

  9. 0:12:15 · watch on youtube.com↗

    Our reading

    A compiler that names every place a change breaks turns refactoring into fixing errors until the compiler stops shouting.

    Their wordsI think this is kind of leads to another way that Rust really helps with reliability, which is that if you're refactoring, I think Rust is really good at telling you all the places you need to update. I've done this sometimes where I would refactor something. I change the code. I change the return type or whatever it is, and then I just fix the compiler errors and until the compiler stops shouting. And then once I've done that, I've updated every place I need to update.
    Interesting
  10. 2 min later

  11. 0:13:47 · watch on youtube.com↗

    Our reading

    The case for Rust is stronger against C++ than against JavaScript, because in C++ an ordinary mistake is usually a security vulnerability.

    Their wordsSo, here I actually think it's even stronger. The thing with C++ is that if you make a mistake, right, in in JavaScript, maybe you take down your server, which is already bad enough, but in C++ when you make a mistake there, now it's actually a security vulnerability most of the time.
    Interesting
  12. 1 min later

  13. 0:14:29 · watch on youtube.com↗

    Our reading

    Memory safety means an entire class of bug is impossible no matter how bad the code is — and it is the class that becomes security vulnerabilities.

    Their wordsMemory safety is this idea that no matter how stupid the code you write is, it's not going to have a certain class of bugs. And this is the, you know, the kind of bug that usually leads into security vulnerabilities.
    Interesting
  14. 4 min later

  15. 0:18:15 · watch on youtube.com↗

    Our reading

    What is unique about Rust is not any one feature but the combination: high-level reliability with no garbage collector, so it runs in kernels and firmware.

    Their wordsI think where Rust is really unique is in the combination of things. So on one hand, it it doesn't have a garbage collector and it it's usable in low-level context like the Linux kernel or firmware or whatever.
    Interesting
  16. 1 min later

  17. 0:19:12 · watch on youtube.com↗

    Our reading

    Garbage collection is a problem for backends too, not only for embedded code: a collection that lands on an incoming request is a latency spike.

    Their wordsEven for back end, it can be a problem because if you have a request incoming right when it checks all of your objects like you have some sort of latency spike where you it takes much longer to to reply. So that's one of the reasons it can be helpful in in back end as well.
    Interesting
  18. 1 min later

  19. 0:20:07 · watch on youtube.com↗

    Our reading

    What trips up newcomers to Rust is not the code but the shape of their data.

    Their wordsI think the most tricky thing people run into is how should you put together your data structures? I mean for your code you can mostly do the same things as you can in other languages. I mean that's not entirely true but the big thing is really the data structures.
    Interesting
  20. 7 min later

  21. 0:27:23 · watch on youtube.com↗

    Our reading

    The guarantee Rust makes is conditional: write no unsafe, and no amount of bad code can produce a memory-safety bug.

    Their wordsWhat Rust ensures is that if you have no use of unsafe, then no matter how stupid your code is, you will never have one of those bugs.
    Interesting
  22. 1 min later

  23. 0:27:53 · watch on youtube.com↗

    Our reading

    The unsafe keyword does not switch the borrow checker off; it only unlocks a few operations you then have to justify yourself.

    Their wordsAnd it's interesting to point out here that unsafe does not disable the borrow checker or anything like that. It just gives you a few more operations you can perform that are not safe in general.
    Interesting
  24. 2 min later

  25. 0:29:42 · watch on youtube.com↗

    Our reading

    Application code should contain no unsafe at all: unsafe is how you add a missing feature to the language, not how you write a server.

    Their wordsSo usually it will never show up in say a backend server. You would have zero uses of unsafe there. Generally when unsafe is used, it's to add a new feature to the language.
    Interesting
  26. 5 min later

  27. 0:34:50 · watch on youtube.com↗

    Our reading

    Rust's least mature area is the front end: write the backend in Rust and the front end in TypeScript rather than shipping Rust to the browser through WebAssembly.

    Their wordsMy opinion is that the least mature area is front end. There have been some attempts to compile Rust to Web Assembly and then run it on the web as a front end as a replacement for TypeScript. But if I was writing a web server, I would totally use Rust for the back end and TypeScript for the front end. I would not really go the web assembly route.
    Interesting
  28. 2 min later

  29. 0:36:59 · watch on youtube.com↗

    Our reading

    A language does not need a benevolent dictator: if the responsible team does not sign off on a change, it does not happen.

    Their wordsHonestly, if the team doesn't sign off on it, it doesn't happen. I mean if something is really contentious contentious or really big it will probably end up being discussed at a conference for example.
    Interesting
  30. 3 min later

  31. 0:39:31 · watch on youtube.com↗

    Our reading

    A design proposal should describe the feature as though it already existed — once as a tutorial and once as reference documentation.

    Their wordsAnd what this is is that in the guide level explanation, you explain your feature as if you were writing a guide as if the feature already existed. And in the reference level explanation, you explain your feature again as if it already existed, but as if it would be in the language reference instead of a tutorial.
    Interesting
  32. 9 min later

  33. 0:48:25 · watch on youtube.com↗

    Our reading

    A language can keep changing without a Python-2-to-3 break, as long as code written under the old and the new rules can be mixed freely in one program.

    Their wordsReally the big idea is to say we want the old code to continue working but we still want to change the language. And so the the difference from other kinds of versions of languages I mean Python 2 version Python 3 comes to mind is that you can totally mix and match in any way you want.
    Interesting
  34. 2 min later

  35. 0:50:28 · watch on youtube.com↗

    Our reading

    The Linux kernel is unique in having thousands of contributors paid to work on it; Rust does well by any other standard and is still nowhere near that.

    Their wordsI would say here that the Linux kernel is truly unique in this particular aspect in that they have thousands of contributors doing it on work time. I actually think that the Rust project is doing pretty well at having people do it and get paid for it like by their employer, but it's nowhere near the to the same extent as as the Linux kernel.
    Interesting
  36. 2 min later

  37. 0:52:23 · watch on youtube.com↗

    Our reading

    You can contribute to the Linux kernel without touching the kernel, by building the language features the kernel is waiting on.

    Their wordsAnother thing that's really cool is you can contribute to the Linux kernel without contributing to the Linux kernel, right? because you might take a Rust language feature we need and implement it and now you've contributed to the Linux kernel indirectly
    Interesting
  38. 2 min later

  39. 0:54:01 · watch on youtube.com↗

    Our reading

    Rust is no longer experimental in the Linux kernel — the maintainers agreed that at their December 2025 summit.

    Their wordsThe big news were that at the Linux kernel maintainer summit, we agreed that Rust is no longer experimental in the kernel. That was really big for us compared to the previous year.
    Interesting
  40. 3 min later

  41. 0:57:23 · watch on youtube.com↗

    Our reading

    Rust may be the best language for AI agents to write, because the compiler gives an agent the feedback that tells it what to fix.

    Their wordsI think the same kind of principle applies with agents in that they can talk to the compiler. It will tell them what to fix. So I guess this could be a case. We we'll see. But Rust could be a pretty promising candidate for to use for agents because they can get more feedback and it's just hard it's harder to to ship certain type of bugs or maybe impossible to have certain type of bugs.
    Interesting
  42. 2 min later

  43. 0:59:20 · watch on youtube.com↗

    Our reading

    Memory-safety bugs are not a skill problem: the mistakes are trivial and there are so many places to make one that even an excellent programmer will.

    Their wordsI mean, that's the thing with memory safety, right? You make some sort of trivial mistake. It it's not some complex thing. It's just you make some trivial mistake and there's a bajillion places you could make it.
    Interesting
  44. 3 min later

  45. 1:02:07 · watch on youtube.com↗

    Our reading

    You learn a programming language by building something in it, not by reading about it.

    Their wordsOther than that, I think honestly the way you learn a language is you have you have a project. You you implement some sort of project with it. I mean maybe some sort of web server or something.
    Interesting