rustc is far from idiomatic. Rust used to be GCd, so the compiler uses a lot of things designed in a GC-esque way but tweaked so that they no longer need a GC.

rustc is far from idiomatic. Rust used to be GCd, so the compiler uses a lot of things designed in a GC-esque way but tweaked so that they no longer need a GC. In general the language has changed a lot, and the compiler source takes some time to catch up completely.