I don't think so. The backend would simply lag behind major releases a bit. It's not going to use all of the compiler internals, so updating it will only be a l

I don't think so. The backend would simply lag behind major releases a bit. It's not going to use all of the compiler internals, so updating it will only be a little extra work if the HIR (or maybe MIR, depending) changes. If Rust has plans on building a large amount of their internal optimizations on MIR, then I would think MIR would be fairly stable too, which makes this even less of an issue. It's going to be a toy project for now. If it works out, it'll be maintained against a specific version of the Rust compiler (stability is important in industry). And if that works out even more, perhaps Rust will accept patches to put it in-tree. Of course, in-tree would be better. But it isn't a requirement. But none of that is important at this point.