Definitely true when using VC++ with C++20 modules and MSBuild.
It also helps not compiling everything from source as many UNIX folks do.
Lol, sorry, but as soon as MSBuild is involved the compiler can be infinitely fast and you'd still need to be waiting for the build. Also the main problem of MSVC is the slow linker, and that isn't fixed by C++ modules. This is also the first time I'm hearing that C++ modules actually help with compilation speed in real world projects - the best I've heard so far is that they're a bit faster than precompiled header but not by much, which simply isn't good enough for typical C++ projects.
The company behind Cadifra UML Editor is quite happy with their migration, the owner keeps posting about their modules experience on Reddit C++.
Microsoft also has CppCon talks on the matter.
All my C++ hobby projects use modules, as I only care about VC++.
You can maybe even do it in C if you are generating code using scripts or abusing macros.
On the other hand, you can write sane C++ (without stdlib) and clang or gcc is able to compile it extremely fast. Because clang and gcc are really fast.
You can write a rust program without dependencies and it would be extremely hard to make it compile slow unless you are abousing generics or procedural macros. But you can write a 100 line webserver using some framework like axum and it will compile really slow. This is not because Rust is slow to compile or rust compiler being slow.
On the other hand you can write a zig file with a single test and compiling it using Release mode takes 3+ seconds on a modern computer because Zig compiler is extremely slow when using LLVM backend. This is also obviosly not because Zig is a slow language to compile since their own backend (non LLVM) has super fast compilation.
