This is my first attempt to contribute to Nix. I'm unsure if pulling in llvmPackages like that is the correct thing, and am generally open to feedback. :)

I'm unsure why this isn't necessary on Linux.

The default compiler on linux is gcc, on darwin it's clang.

I'm unsure if pulling in llvmPackages like that is the correct thing

It's no massive sin, it's just in this case instead of making this conditional on stdenv.isDarwin, I'd instead test stdenv.cc.isClang, because it means if some linux person tries to build this with clang it'll work. Probably.

Or if a darwin person tries to build it with gcc, I guess...

Also, welcome!

The default compiler on linux is gcc, on darwin it's clang.

Ah, yes. That would explain it. It might also explain a few other failures I saw when looking through the Darwin build failures that looked like syntax errors. I bet they only compile with gcc.

I'd instead test stdenv.cc.isClang, because it means if some linux person tries to build this with clang it'll work. Probably.

And, yeah, that then seems the reasonable answer. Thanks!

I've made the change locally and am rebuilding it to verify; I'll push an update shortly.

You'll probably find that it won't rebuild because it will evaluate down to exactly the same thing.

Yeah, I had to rm the result and garbage collect to force it to rebuild. Thanks for the advice and the merge!

In such cases, you don't generally need to bother with a rebuild. In weird cases where you do (maybe debugging a randomly unreliable build?) you can use nix-build's --check flag.

Ah, cool. I thought that might be the case but wanted to be certain I wasn't breaking anything.