[jvillasante]

What does incremental compilation have to do with writing your own compiler from scratch? Isn't Rust supports incremental compilation as does every language out there?

[pbaam]

I guess he means that in order to achieve incremental compilation they need to write their own code generation and linker for every architecture and format. This is needed because incremental compilation here doesn't just mean storing object files in a cache directory (which has always worked that way). They also want to cache every analyzed function and declaration. So they have to serialize compiler state to a file. But after analysis is done, LLVM will start code generation from the beginning (which is the time expensive thing, even in debug builds)

[jvillasante]

Yes, but isn't that an implementation detail? Shouldn't they prioritize getting to 1.0 (the language itself) and then work in implementation details like that? I mean, It's a monumental task to write compiler and linker from scratch!

[zellyn]

They want incremental compilation at the function level. So if you change a function, you recompile just that function. This necessitates a custom linker (indeed a custom linking strategy), and (I think?) a custom compiler.