Comment by pron

> I kind of discovered "why Rust" from first principles and from then on I was hooked.

I get it. The language certainly does appeal to some people, and I can understand why, just as I understand why it does not appeal to others.

> I found myself wondering why I had to keep track of lifetimes, nullability etc in my head when it was so easy to mess those up.

And I agree with that, but my conclusion (after decades of experience with low-level programming) is somewhat different: Don't reach for a low-level language unless precise low-level control over the hardware is the exact thing you're after. And when that is the case, I find that safe Rust doesn't offer the control I need, and unsafe Rust (and/or a lot of custom code) is not what I want to use.

> Maybe if you're willing to run Java/C# JIT you might find some wins

Of course I use the JIT. That's exactly what it's for. Now, I don't care if the buffer from which the CPU reads instructions is memmapped from a file or generated by a JIT, but I do know that some people like the "single native file experience". To that end, we're working with Google to add a small feature to the JDK that would allow it to link the JVM, other native libraries, and Java classes into a single native executable (it's still going to JIT the Java code, but you'd be launching a "native binary").

> (skeptical it's faster across the board)

I wouldn't say it's faster across the board. You sometimes can write large programs in C++ (or Rust) that match and even exceed Java's performance, but it gets harder and harder the larger the program is. On average, I find that the "effort per performance" is, on average, significantly lower in Java in large programs. And it's not just the JIT. Another weak point of low level languages is that their pointers can't move, which means they can't use moving collectors, which also offer superb efficiency, again, mostly in large programs when you have lots of objects of varying sizes and lifetimes (especially now when we no longer have GC pauses).

> but you also don't need dynamic dispatch in performance-critical areas

You certainly don't start out needing it. Over time, however (and important codebases last at least 15-25 years), it either creeps in or it affects sufficiently many less critical paths to make an impact. You can try and re-architect things, but it takes a lot of effort (and it's this evolution effort that was a major reason for C++'s decline).

> But we see even experienced professionals making mistakes with low level languages

Absolutely, but my prescription would be to avoid low level languages altogether, and that has indeed been the industry's trajectory, and it's continuing. And when you absolutely do need to kind of control that low level languages offer, language complexity can also cause (or help hide) mistakes in code that is often very subtle, and the added safety, which is partial at best in those situations, isn't enough to offset that. Again, this isn't universal, but there are reasons to avoid Rust in low level code that are just as good as the reasons to pick it, and so different people will choose differently.

BTW, I've never worked on a browser, and it may well be the Rust is the best language for that, but I would be very curious to try Java. First, modern browsers run a lot of JS so you have a JIT and a GC, anyway, and so it might be both easier and more efficient to have everything use the same GC, and while process isolation would have required Java to re-JIT the rendering pipeline, Java is about to allow sharing JITted code (and even caching it from one run to the next) so that there would be no need to warm up the same code over and over.