TWiR quote of the week

I used to think that most amazing thing about Rust was that it was able to take solid research and apply it to a system that has quickly gained industry adoption.

I no longer think that. Rust is a byproduct of the governance model, it is the governance model that enabled a group of people to create Rust. And the governance model is the most valuable technology created from the Rust experiment.

u/fullouterjoin on reddit:


On the topic of reframing UB, I was reminded of an article about the mechanics of oaths and vows in historical cultures.

When a programmer writes get_unchecked , we can imagine them wanting to promise the compiler that they uphold its preconditions. But since the compiler is normally not so trusting of unproven assertions, the programmer swears an oath that their argument is in bounds.

The compiler, seeing such a solemn commitment, treats the programmer's word as true and optimizes accordingly. The compiler is so thoroughly convinced that it never even entertains the possibility of doubting the programmer's oath.

But if the programmer has sworn falsely, then they might well suffer divine retribution in the form of nasal demons — or worse, subtly baffling program behaviour.

unsafe is an oath by u/scook0 (I solemnly swear as a keyword when?)


I think, this is a very interesting insight which probably worth sharing with the community.

A tempting alternative to the onboarding problem is to spin off a small sub-team of budding Rust experts to work on mission critical components that require Rust levels of performance or type safety. This was a mistake we made on the Magic Pocket project where a handful of engineers rewrote the storage engine in Rust while the rest of the team continued building the rest of the system in Go. This split was necessary when the Rust components were a small skunkworks project but it persisted for years afterwards.

The Rust components were a victim of their own success — they worked well, didn't require much maintenance, and by the time the original authors left the team to work on Nucleus there weren't many engineers left who were experts in these very-large systems. This slowed innovation on the Rust components for a period of time and left the remaining team with mixed feelings about the use of Rust to begin with.

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The design of the safe/unsafe split means that there is an asymmetric trust relationship between Safe and Unsafe Rust. Safe Rust inherently has to trust that any Unsafe Rust it touches has been written correctly. On the other hand, Unsafe Rust cannot trust Safe Rust without care.

As an example, Rust has the PartialOrd and Ord traits to differentiate between types which can "just" be compared, and those that provide a "total" ordering (which basically means that comparison behaves reasonably).

BTreeMap doesn't really make sense for partially-ordered types, and so it requires that its keys implement Ord . However, BTreeMap has Unsafe Rust code inside of its implementation. Because it would be unacceptable for a sloppy Ord implementation (which is Safe to write) to cause Undefined Behavior, the Unsafe code in BTreeMap must be written to be robust against Ord implementations which aren't actually total — even though that's the whole point of requiring Ord .

From the very first page of the Rustonomicon, itself cited by Gankra in PR#3197 Clarify that RFC1520 does not permit the compiler to replace calls to Clone::clone with a memcpy.


There's a constant focus on backward compatibility, but the (equally constant) feature creep will inevitably break it. English hasn't moved from version 3.x for centuries, and we still have multiple redefined keywords, many modern compilers have dropped support for outdated constructs which -- though legal -- haven't been in use for ages, and in fact the very language has several different implementations with varying levels of mutual compatibility.

-- Birion as one of several fun replies to "The only consistent conclusion is that English is a weird language that needs a significant overhaul." @


(On maybe not using async).


Important crab-related diagnostics improvement shipping in nightly

error: Ferris cannot be used as an identifier
 --> src/
2 |     let 🦀 = 123;
  |         ^^ help: try using their name instead: `ferris`
3 |
4 |     for i in 0..🦀 {

@matklad in Rust will revolutionize ecosystem of high level language?


So I think this is what many Rust developers means when they say zero trust cost abstractions.

Rainer Stropek in Traits, not your grandparents' interfaces.

Please do not publish this one, (EDIT2: I don't think it's worth publishing) I just fond the slip of the tongue very funny!

EDIT: this post has been flagged as off-topic. I would have like to know why. This is a citation, about Rust, from a very interesting conference, and I selected it because it was funny. And while I think its not worth publishing it in TWIR because it doesn’t bring any new insight about Rust, I think it has its place in this thread for the pleasure of people that propose and vote for TWIR citations.


This thread is for submitting Quotes of the Week for This Week in Rust. If you don’t want your quote to be published, then it probably doesn’t belong here (though TWiR quotes that are just funny have been published before).


By no means a "learning" kind of quote, but…

I just discovered an absolutely critical bug in the Rust logo:

Screenshot 2021-12-20 at 23 42 01

It's not symmetrical! The inner and outer circle of the gear don't even have the same center.

from Mara Bos here

(yes, this has somehow gone years without anyone noticing)


Oh come on, I was just about to go to sleep...



(The elision there is to avoid making any commentary on the actual issue in that topic part of the quote; in general, I think we should avoid highlighting quotes that directly comment on one side of an active topic, so I left that part out.)


I’m saddened to think that because this industry has an obsession with making programming accessible to the lowest common denominator, expressive and innovative languages like Rust will fall by the wayside, and we’ll all be writing code in languages like Go and Python in the future because they’re “easy” and even high schoolers can learn them in a couple days.

By booleandilemma on hacker news


A nice reminder that sometimes the shortest answer isn't the best one.


Fun fact if you repeat "Thread scoped private field injection" 3 times to a Mirror you will summon a demon.

-- MyLifeAsSinusOfX @

For any language SomeLang™:

The context of that thread is already interesting on its own, but I even think that taking that quote seriously / in a first degree fashion is actually meaningful: for some codebases written from scratch and which developed features out of an initially thin core, the newly obtained perspective on the problem ought to make rewriting that codebase "from scratch" yield cleaner, leaner, and potentially faster code (and back to that RiiR thread, hence why sometimes the Ri part may be just as important if not more important than the iR part).



The error message code will at one point become sentient and decide to send a robot back in time to save mankind from skynet [...]

(Rust 2021 – Looking Back and Forth — Llogiq on stuff)


I performed an extremely scientific poll on twitter, and determined this is not how it's pronounced

Well, it really is Vec<T, A>, pronounced Veck-tah. :stuck_out_tongue:

Look, I moved away from Boston to avoid this sort of thing :laughing:.

-- thomcc and the8472 in Remove pronunciation guide from Vec<T>


"For me, the joy of Rust comes from the fact that I can write code that represents the mental model I have of the problem" - Jon Gjengset, 2022-01-01 Q&A/AMA/Whatchamacallit.

I resonated so strong with this statement. This is the reason why I find joy in Rust and I evangelize about it.