It's unfortunate that the enum-based solution doesn't work, but that particular example can be made "optimal" (at least, as good control flow as LLVM can get th

It's unfortunate that the enum-based solution doesn't work, but that particular example can be made "optimal" (at least, as good control flow as LLVM can get this code: the same as clang, not GCC), by using a rather unpleasant series of loops and labelled breaks: https://godbolt.org/z/sQ1nH8 https://godbolt.org/z/sQ1nH8 (rustfmt'd version: https://play.rust-lang.org/?gist=b1091e0c583b88f27bf1eaeae3a670f0&version=stable&mode=debug&edition=2015 https://play.rust-lang.org/?gist=b1091e0c583b88f27bf1eaeae3a...). This doesn't work in general, and is ... impossible to maintain, but it's not an unreasonable approach for generated code.