Mostly orthogonal, but I wish we have the similar separation in the sources in rust-lang/rust itself. I imagine something like src/runtime for libstd, libcore, libtest, and src/compiler for various rustc bits.
I would also prefer if llvm and other huge repost would be in a different place than the directory where all the sources of the Rust compiler are. I have to use ripgrep+.ignore file to grep for anything in the rust sources because otherwise it tries to go through all LLVM sources which are huge.
Telling a beginner to search for something in the src/ directory isn't as simple as suggesting them to just grep for it. You need to tell them to get ripgrep, add an ignore file, and only then can they properly search the compiler source code..
FWIW I’ve been using rg foo src/lib* to search the standard library and rustc and filter out LLVM. (This not to argue against a change in the directory structure.)