Someone just pointed this out to me.
It is an extension of Racket used for verification and synthesis.
In this video https://www.youtube.com/watch?v=KpDyuMIb_E0 at minute 42 they present some applications of the DSL which seem interesting.
I will need to dive more into this, but this could be of interest to @voelter and @sergej , given the discussion on Racket