Rust's Cover (replacing the Javas in http://www.paulgraham.com/javacover.html for lols)

June 2019

This essay developed out of conversations I've had with several other programmers about why Rust smelled suspicious. It's not a critique of Rust! It is a case study of hacker's radar.

Over time, hackers develop a nose for good (and bad) technology. I thought it might be interesting to try and write down what made Rust seem suspect to me.

Some people who've read this think it's an interesting attempt to write about something that hasn't been written about before. Others say I will get in trouble for appearing to be writing about things I don't understand. So, just in case it does any good, let me clarify that I'm not writing here about Rust (which I have never used) but about hacker's radar (which I have thought about a lot).


The aphorism "you can't tell a book by its cover" originated in the times when books were sold in plain cardboard covers, to be bound by each purchaser according to his own taste. In those days, you couldn't tell a book by its cover. But publishing has advanced since then: present-day publishers work hard to make the cover something you can tell a book by.

I spend a lot of time in bookshops and I feel as if I have by now learned to understand everything publishers mean to tell me about a book, and perhaps a bit more. The time I haven't spent in bookshops I've spent mostly in front of computers, and I feel as if I've learned, to some degree, to judge technology by its cover as well. It may be just luck, but I've saved myself from a few technologies that turned out to be real stinkers.

So far, Rust seems like a stinker to me. I've never written a Rust program, never more than glanced over reference books about it, but I have a hunch that it won't be a very successful language. I may turn out to be mistaken; making predictions about technology is a dangerous business. But for what it's worth, as a sort of time capsule, here's why I don't like the look of Rust:

1. It has been so energetically hyped. Real standards don't have to be promoted. No one had to promote C, or CLIM, or HTML. A real standard tends to be already established by the time most people hear about it. On the hacker radar screen, Perl is as big as Rust, or bigger, just on the strength of its own merits.

2. It's aimed low. In the original Rust white paper, Graydon Hoare explicitly says Rust was designed not to be too difficult for programmers used to C. It was designed to be another C++: C plus a few ideas taken from more advanced languages. Like the creators of sitcoms or junk food or package tours, Rust's designers were consciously designing a product for people not as smart as them. Historically, languages designed for other people to use have been bad: Java, PL/I, Pascal, Ada, C++. The good languages have been those that were designed for their own creators: C, Smalltalk, Lisp.

3. It has ulterior motives. Someone once said that the world would be a better place if people only wrote books because they had something to say, rather than because they wanted to write a book. Likewise, the reason we hear about Rust all the time is not because it has something to say about programming languages. We hear about Rust as part of a plan by Mozilla to undermine Microsoft.

4. No one loves it. C, Python, Smalltalk, and Lisp programmers love their languages. I've never heard anyone say that they loved Rust.

5. People are forced to use it. A lot of the people I know using Rust are using it because they feel they have to. Either it's something they felt they had to do to get funded, or something they thought customers would want, or something they were told to do by management. These are smart people; if the technology was good, they'd have used it voluntarily.

6. It has too few cooks. The best programming languages have been developed by large groups. Rust seems to be run by a BDFL. If it turns out to be a good language, it will be the first time in history that a BDFL has designed a good language.

7. It's bureaucratic. From what little I know about Rust, there seem to be a lot of protocols for doing things. Really good languages aren't like that. They let you do what you want and get out of the way.

8. It's pseudo-hip. Mozilla now pretends that Rust is a grassroots, open-source language effort like Perl or Python. This one just happens to be controlled by a giant company. So the language is likely to have the same drab clunkiness as anything else that comes out of a big company.

9. It's designed for large organizations. Large organizations have different aims from hackers. They want languages that are (believed to be) suitable for use by large teams of mediocre programmers -- languages with features that, like the speed limiters in U-Haul trucks, prevent fools from doing too much damage. Hackers don't like a language that talks down to them. Hackers just want power. Historically, languages designed for large organizations (PL/I, Ada) have lost, while hacker languages (C, Lisp) have won. The reason: today's teenage hacker is tomorrow's CTO.

10. The wrong people like it. The programmers I admire most are not, on the whole, captivated by Rust. Who does like Rust? Hipsters, who don't know one language from another, but know that they keep hearing about Rust in the press; programmers at big companies, who are amazed to find that there is something even better than C++; and plug-and-chug undergrads, who are ready to like anything that might get them a job (will this be on the test?). These people's opinions change with every wind.

11. Its daddy is in a pinch. Mozilla's business model is being undermined on two fronts. Dynamic languages, of the same type used in concurrency experiments, are now more than fast enough for servers. And Chromium seems to be at least as good a browser. Mozilla's advertising implies that you need Rust for concurrent applications. If this were true, Google would be first in line to use Rust; but when I worked there, the servers were all C boxes. This bodes ill for Mozilla's future. If Mozilla runs into trouble, they could drag Rust down with them.

12. The DoD likes it. The Defense Department is encouraging developers to use Rust. This seems to me the most damning sign of all. The Defense Department does a shite job of defending the country, but they love plans and procedures and protocols. Their culture is the opposite of hacker culture; on questions of software they will tend to bet wrong. The last time the DoD really liked a programming language, it was Ada.

Bear in mind, this is not a critique of Rust, but a critique of its cover. I don't know Rust well enough to like it or dislike it. This is just an explanation of why I don't find that I'm eager to learn it.

It may seem cavalier to dismiss a language before you've even tried writing programs in it. But this is something all programmers have to do. There are too many technologies out there to learn them all. You have to learn to judge by outward signs which will be worth your time. I have likewise cavalierly dismissed Cobol, Ada, Visual Basic, the IBM AS400, VRML, ISO 9000, the SET protocol, VMS, Novell Netware, and CORBA, among others. They just smelled wrong.

It could be that in Rust's case I'm mistaken. It could be that a language promoted by one big company to undermine another, designed by a committee for a "mainstream" audience, hyped to the skies, and beloved of the DoD, happens nonetheless to be a clean, beautiful, powerful language that I would love programming in. It could be, but it seems very unlikely.