The GCC compiler collection has been hit and miss though. Nobody uses gcj for example. I sort of doubt that they'll be able to implement a good compiler for a language that doesn't even have a standard without that implementation going wildly out of date in the future, just like what happened with Java.

Since OpenJDK was released there isn't much point maintaining GCJ.

There's two different methods by which Rust support can be added to GCC: adding a Rust frontend to GCC and adding a GCC backend to the Rust compiler (rustc_codegen_gcc). The latter approach would not be (as?) susceptible to implementation divergence as an independent frontend.