TWiR quote of the week


About code using immediately-invoked closure like if let Err(e) = (|| -> io::Result<()>{…})():

Haskell has do notation; we have don’t notation


From, comparing Rusts safety guarantees with seat-belts.

Say the same thing about seatbelts in a car. If you don’t plan to have accidents, why do you need seatbelts?

Car accidents, like mistakes in programming are a risk that has a likelihood that is non-zero. A seatbelt might be a little bit annoying when things go well, but much less so when they don’t. Rust is there to stop you in most cases when you try to accidentally shot yourself into the leg, unless you deliberately without knowing what you are doing while yelling “hold my beer” (unsafe). And contrary to popular belief even in unsafe blocks many of Rust’s safety guarantees hold, just not all.

Just like with the seatbelt, there will be always those that don’t wear one for their very subjective reasons (e.g. because of edge cases where a seatbelt could trap you in a burning car, or because it is not cool, or because they hate the feeling and think accidents only happen to people who can’t drive).


TWiR 273 had some good reads again!

This one aptly summarizes just how much our consolidation work has paid off!

… the experience I had in 2019 was dramatically better than the first time I touched the language. After a month I’m feeling very comfortable, and looking forward to writing more.

Ryan Ragona on his blog post: Learning Rust in 2019


/u/Quxxy on Reddit:

Can you eli5 why TryFrom and TryInto matters, and why it’s been stuck for so long ? (the RFC seems to be 3 years old)

If you stabilise Try{From,Into}, you also want implementations of the types in std. So you want things like impl TryFrom<u8> for u16. But that requires an error type, and that was (I believe) the problem.

u8 to u16 cannot fail, so you want the error type to be !. Except using ! as a type isn’t stable yet. So use a placeholder enum! But that means that once ! is stabilised, we’ve got this Infallible type kicking around that is redundant. So change it? But that would be breaking. So make the two isomorphic? Woah, woah, hold on there, this is starting to get crazy…

*new person bursts into the room* “Hey, should ! automatically implement all traits, or not?”

“Yes!” “No!” “Yes, and so should all variant-less enums!”

Everyone in the room is shouting, and the curtains spontaneously catching fire. In the corner, the person who proposed Try{From,Into} sits, sobbing. It was supposed to all be so simple… but this damn ! thing is just ruining everything.

… That’s not what happened, but it’s more entertaining than just saying “many people were unsure exactly what to do about the ! situation, which turned out to be more complicated than expected”.


mikesu9: What is the ! type?
LousyBeggar: The never type for computations that don’t resolve to a value. It’s named after its stabilization date.

LousyBeggar, on reddit

Announcing Rust 1.33.0

A quote on the topic of trust, and by extension, security.


Nobody contributed. Rust started writing itself to avoid human bugs.

Asimov needs a 4th law to #![forbid(unsafe_code)] .

– rat9988 and CUViper on Reddit.


– Rust’s ownership is difficult.
– Yes, ownership is difficult. For such a difficult thing, you (are going to) ever check by hand rather than having machine do it for you.

@Cryolite on Twitter (Japanese)


From normally-aspirated::<fish> on the (unofficial) community discord:

Rust is OOP
Ownership Oriented Programming


“all the ergonomic improvements in rust 2018 are really messing up my book that consists entirely of running face-first into compiler errors so i can explain concepts.” – Alexis Beingessner, author of “Learning Rust With Entirely Too Many Linked Lists”


C++ prevents “thing without pointer” and Rust prevents “pointer without thing”

@RibeiroLivio on twitter


I quite liked TomP’s answer:

One major difference is that Ada was created at a time when most military computers were single-core with in-order sequential execution and no cache. Although limited SIMD existed, any other concurrency was very coarse-grained. That’s the underlying execution model for C, Pascal, C++, etc.

Rust was created to address the complexity of multi-core processors with multi-level cache hierarchies where computational efficiency may require much concurrency. In my experience few humans are capable of error-free design and implementation of highly-concurrent systems unless they employ tooling that flags their errors in conceptualization or implementation.


Confusion is a product type.

—/u/casual-cryptarch on explaining traits and references at the same time

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Yes, Markdown is like Frankenstein’s monster before applying electricity, and Org-mode is the monster after applying electricity.

-/u/jimuazu in this thread about a parser for Emacs’ Org-Mode format

(not really a quote about Rust, but I found it pretty enjoyable nonetheless)


A compile_fail test that fails to fail to compile is also a failure.

The trybuild README.


Yes, this adds to Rust’s “wierdness budget”, but this is doing it for the right reason: discovering a way to solve a problem that many programming languages have, but few have really tackled.

jcsoo on await syntax (on internals)


The big gorilla 3D game framework. Apparently it actually works.

SimonHeath on Amethyst

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Never play drinking games with the rust compiler. It will destroy you and show you how sorry of a developer you are!

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Just the presence of well integrated Algebraic Data Types (ADTs) makes an incredible amount of difference. They are used to represent errors in a meaningful and easy to understand way (Result<T>), are used to show that a function may or may not return a meaningful value without needing a garbage value (Option<T>), and the optional case can even be used to wrap a null pointer scenario in a safe way (Option<Ref<T>> being the closest to a literal translation I think).

That’s just one small feature that permeates the language. Whatever the opposite of a death-of-a-thousand-cuts is, Rust has it.

tomcatfish on “… how (Rust) takes basic concepts from low to high level without bothering me or killing performance…”