go (FunTy a b) = go a `plusNameEnv` go b
go (PredTy (IParam _ ty)) = go ty
go (PredTy (ClassP cls tys)) = go_tc (classTyCon cls) tys
+ go (PredTy (EqPred ty1 ty2)) = go ty1 `plusNameEnv` go ty2
go (ForAllTy _ ty) = go ty
- go _ = panic "tcTyConsOfType"
go_tc tc tys = extendNameEnv (go_s tys) (tyConName tc) tc
go_s tys = foldr (plusNameEnv . go) emptyNameEnv tys