We present a vision of genetic improvement firmly embedded in, and supported by, programming languages. Genetic improvement has already been envisioned as the next compiler, which would take human written programs as input and return versions optimised with respect to various objectives. As an intermediate stage, or perhaps to complement the fully automated vision, we imagine genetic improvement processes that are hinted at and directed by humans but understood and undertaken by programming languages and their runtimes, via interactions through the source code. We examine existing similar ideas and examine the benefits of embedding them within programming languages.