TWiR quote of the week


On #rust-internals wrt.

durka42 IMO the name “dangling” is scary enough :slight_smile:
Havvy gives durka42 a ptr::dangling::<Candy>().
durka42 declines to unwrap() it


A brilliant observation by @kickass_turing on reddit about Rust code being refactoring friendly:

Also the way I see it is that Rust makes problems local.


Another nice example of the “lisp effect”, where learning one language makes you better in another :slight_smile:


I think x & & y is still, unfortunately, different from x && y.

See: (x & & y is really just x & y, which doesn’t short-circuit boolean logic)


I’d think & & should just flat-out be an “expected expression, found …” error like it is with 1 + + 2.

x && y makes sense and x & &y is meaningful as "bitwise AND together x and the auto-deref-coerced value of y" , but x & & y looks like it’s guaranteed to be a typo-induced bug.


Such arbitrary introduced whitespace sensitivity is the death of automatically generated code, though (think macros).


Point, but it should at least be a warning. (And that’s assuming that rustc can’t just handle macro-generated code differently in that case and force any re-serialization of the AST back to the spaceless form.)

When I look at 5 & & 5, I don’t see 5 BitAnd Borrow(5). My intuition is to see it as some weird no-op pass-through special-case of (5 BitAnd) BitAnd 5 or 5 BitAnd (BitAnd 5).

Heck, until I actually looked into what x & & y was doing, I firmly believed that the compiler only parsed & as a borrow operator if there was no whitespace between it and what follows.

(ie. “&'s status as a unary operator is determined by whitespace” won out in my intuition despite my knowing that - as a unary operator is not whitespace sensitive in Rust. I believed that separating them was like writing ma tch { rather than match {)

Who knows how many other “at most, one semester of C and C++ combined back in the hazy days of university” programmers will make that mistake.


I know what you mean, but for me this is just too much guesswork on the compiler’s part. As far as I know, whitespace between tokens does not matter anywhere in Rust right now. (Also, not all generated code comes from macros.)

It’s not like making the mistake will get you a typechecking program that only misbehaves at runtime. In contrast to similar issues in dynamic languages, such as the “interesting” case a in b < c in Python.


[please insert kind reminder to move these discussions into a new thread]
Thank you very much ladybugs and gentlecats.


“Although rusting is generally a negative aspect of iron, a particular form of rusting, known as “stable rust,” causes the object to have a thin coating of rust over the top, and if kept in low relative humidity, makes the “stable” layer protective to the iron below”



I assumed someone made a recent change in Wikipedia in a jest.
So I tracked the change in Wikipedia, and it is more than a year old.
The WIkipedia diff.


No, that is a real thing. It is sometimes used to protect steel infostructure. Although it has gotten less common as it does not hold up as well in the wild as it does in the lab.

I do love how ambiguous that quote is. It can so easily be read as using rust as a metaphor for Rust.

<mbrubeck> I think that I shall never see
<mbrubeck> a poem as pretty as Result<Option<T>,E>

An english language quesion

Every great language needs a Steve.

Someone from hackernews about @steveklabnik:

By the way, let me tell a personal story of how I’ve actually got involved with Rust… This happened shortly after 1.0. At that time, I’ve just finished the year-long C++ course for master’s students at my university. The course instructor was really really great, and I’ve got a solid understanding about major moving parts of the language. I’d read “the C++ programming language” book before, and I’d even pushed some semi-production C++ code, but, after working with the course instructor, I came to realization that I hadn’t knew a thing about C++ before! So, my conclusion was that everyone who wants to touch C++, should really attend a university and take a proper master’s-level C++ course.

And then, Rust comes into my life. I open a nice minimalist webside, and I see a link to “The Rust Book” there. I click the link and I see the official book which just goes and teaches you how to use the language! So, I’ve read the book and I could program in Rust! (granted, I needed quite a lot of practice to stop fighting the borrow checker and to learn that you shouldn’t put extern crate rand into each and every of your modules, but these are details :slight_smile: )

The fact that there is an official book which you can just read and be able to use the language astonishes me even today!

Thanks a lot to all of you, who contributed to Rust documentation in any form, and especially to @steveklabnik! :heart:


If C is like playing with knives and C++ is like juggling chainsaws then Rust is like parkour wearing protective gear while suspended from strings. It may look ridiculous at times, but you can do all sorts of awesome moves that would be damn scary or outright impossible without it.

u/llogiq on r/rust


Dialog between @matklad and @arielb1 here:

Joke that it looks like SoA, ECS, and that we should build compiler like a game engine so that we can rewrite a browser like a game engine.

The compiler itself is already an ECS, this is just pushing stuff to the parser too.


Honestly, after more than 25 years of C (and C++), I’ve become very frustrated with the average C code I seen in the wild. OpenSSL is fairly typical, in a lot of ways. So much C code has buffer overflows, numeric overflows, memory leaks, double frees, undefined behavior, and an an endless number of bugs. There are exceptions—djb’s code is quite good, dovecot seems reasonable, OpenBSD audits aggressively—but when I dive into most C code, I expect problems… I’m tired. I don’t want to rely on programmers practicing constant, flawless vigilance.

u/emk on r/rust


moz irc, #rust

15:40 < Ske> Oh, that compiles
15:40 < Ske> This is gonna bite me in the ass sooner or later isn’t it

very zeitgeist imo


Anything that will make wasm nicer will be awesome, but honestly, I’m thrilled with what we’ve got. It feels absolutely insane that I can just compile this language that’s basically the opposite of JavaScript and it’s running in the browser.

Tomas Sedovic at

Suggested by u/ErichDonGubler


Rust: spend your lifetime thinking about lifetimes.

– /u/heysaturdaysun