Comment by pierrelgol
10 days ago
That's true, but then there's also the case of working on the zig compiler which is roughly a million loc, and with `--watch -fincremental` you can get 200ms recompile even if you change some of the most called function. Meanwhile even a 5k-10k rust project can take a 30s to recompile on minor changes. So the impact on velocity can be quite high, I love both languages, but the Zig compiler is undeniably faster than the Rust compiler and by multiple orders of magnitudes.
Rust also has incremental compiling and is pretty fast, I haven't experienced 30 second compile times when using cargo watch. See also, cranelift, which is supposed to make compile times even faster.
The problem is not just that Rust takes a few seconds longer once. It compounds across the edit/debug cycle. If you make around 800 save/check iterations in a day, then a 2.5–3.5s feedback loop costs roughly 34–48 minutes of waiting per day. The same number of iterations at 200ms costs about 2.8 minutes.
So the practical delta is around half an hour to three quarters of an hour per day, or multiple hours per week. That directly affects flow state and experimentation speed. over the span of a month that's 2 full days worth of work waiting for the compiler. Or if you take my company's evaluation of the average engineer's hour cost it's roughly 2550 per month or almost 30k per year, obviously it's a bit exaggerated, you don't spend a full year refactoring and working like that, but even a tenth of that is still a big lump of money if you scale it to a few teams.
Now it needs to be taken with a huge pinch of salts because Rust provides other benefits that offsets the fact that it's painfully slow to compile, but still worth noting
from my own testing even their incremental on a codebase 10x smaller than the Zig compiler like Helix the text editor, on my machine almost all changes take 2/3s and with cranelift it's like 4/5s.
So it's definitely a faster feedback loop and honestly completely bearable, but it's not 200ms.