Indeed, this is part of Virgil's default test run (and presumably most self-hosted compilers'). If the question is about adding new features to the language, t

Indeed, this is part of Virgil's default test run (and presumably most self-hosted compilers'). If the question is about adding new features to the language, then the process is: 1. Add the new feature to the (source of the) new compiler in a way that doesn't break any existing feature. 2. Cement the new feature in with extensive tests. 3. Bootstrap the new compiler and stable-rev it (in Virgil, that means checking in the new compiler's binary into the repo). 4. Work on other things for a while; either optimizations in the compiler or applications, to shake out bugs. 5. Bootstrap and stable-rev again. 6. Gently start using the new feature in the compiler source itself.