[prologist]

Thanks. The Shen language takes this to its logical conclusion (pun intended) and implements a fully Turing complete type system. Types are specified with sequents which are essentially Prolog relations using a slightly different notation.[1]

1: https://shenlanguage.org/OSM/Recursive.html

[divs1210]

Yes! I have played with Shen before.

IIRC the type checker is literally a Prolog.