Very useful tool. Been using this for years at this point.
The fact that the compiler can’t/doesn’t do this itself is, in retrospect, such a damn warning sign.
This is exactly the sort of thing C++20 modules will fix. So it’s not like the language/compiler people have been ignoring this. (And I believe modules have been in the works for years.)
I think we had used this to improve Firefox build times “recently”, but only found a blog post from 2013. Oops. Not so recent, then?