Did you mean "What is the TcHsSyn counterpart to TcMType.zonkTcTyVar"?

D'oh. Yes, I did.

But it's never a bad idea to document more.

I've documented all the wisdom from here in this wiki page [1]! Feel free to edit it if there are any corrections to be made. Ryan S. ----- [1] https://gitlab.haskell.org/ghc/ghc/wikis/commentary/compiler/tying-the-knot/...