Rust does have incremental rebuilds, yes.

Folks have worked tirelessly to improve the speed of the Rust compiler, and it's gotten significantly faster over time. However, there are also language-level reasons why it can take longer to compile than other languages, though the initial guess of "because of the safety checks" is not one of them, those are quite fast.

> How slow are we talking here?

It really depends on a large number of factors. I think saying "roughly like C++" isn't totally unfair, though again, it really depends.

People do have cold Rust compiles that can push up into measured in hours. Large crates often take design choices that are more compile time friendly shape.

Note that C++ also has almost as large problem with compile times with large build fanouts including on templates, and it's not always realistic for incremental builds to solve either especially time burnt on linking, e.g. I believe Chromium development often uses a mode with .dlls dynamic linking instead of what they release which is all static linked exactly to speed up incremental development. The "fast" case is C not C++.