I came across this yesterday, and thought it was interesting: https://www.rapid-scheme.org/ On the about page, it points out the benefits of doing this sort of metacircular implementation. One of the points it makes is: "Compiler writers can use Rapid Scheme as a front-end of a standalone implementation of R7RS. In particular, it should be relatively easy to combine an existing implementation of an earlier report such as R5RS with Rapid Scheme to produce a stand-alone implementation of R7RS." And lo! Gambit Scheme can now compile R7RS code: https://www.rapid-scheme.org/news/backend/porting/2016/07/09/rapid-gambit.ht... -Joe