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