The very idea of having compilation unit boundaries look like project boundaries squicks me :/... the lightweight compilation unit structure C/C++ has--with the ability to elide information but the requirement that it be prototyped--frankly always seemed like the perfect tradeoff, and it generally means that projects are able to be compiled in massively parallel environments as all of the dependencies are explicit. This is why distcc is such a trivial project to just drop on almost C codebase, and is why I have been able to get our builds doing like 100x parallel compiles on AWS Lambda (and like, before someone tries to claim that header file bloat somehow prevents this: it doesn't, and build engineers do massively parallel build farms for C/C++ all the time, and it is only in some specific corner cases of C++ projects defined entirely as templates where this comes up, and even then there are trivial techniques you can use to help break the translation units apart). Every time a new language comes out and tries to "fix" translation units by adding tons of cross-file information dependencies without the explicit definition vs. declaration difference I kind of roll my eyes as I know there's almost no chance the build is ever going to fast, and these "we need all the code at once to even begin to analyze it" languages are the worst :(.