Tidying could cause ill-kinded types
I found (Trac #14175) that the tidying we do when reporting type error messages could cause a well-kinded type to become ill-kinded. Reason: we initialised the tidy-env with a completely un-zonked TidyEnv accumulated in the TcLclEnv as we come across lexical type-varialbe bindings. Solution: zonk them. But I ended up refactoring a bit: * Get rid of tcl_tidy :: TidyEnv altogether * Instead use tcl_bndrs :: TcBinderStack This used to contain only Ids, but now I've added those lexically scoped TyVars too. * Change names: TcIdBinderStack -> TcBinderStack TcIdBinder -> TcBinder extendTcIdBndrs -> extendTcBinderStack * Now tcInitTidyEnv can grab those TyVars from the tcl_bndrs, zonk, and tidy them. The only annoyance is that I had to add TcEnv.hs-boot, to break the recursion between the zonking code and the TrRnMonad functions like addErrTc that call tcInitTidyEnv. Tiresome, but in fact that file existed already.
Showing with 127 additions and 81 deletions