zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
zipTyEnv tyvars tys
  | debugIsOn && (length tyvars /= length tys)
  = pprTrace "zipTyEnv" (ppr tyvars $$ ppr tys) emptyVarEnv
  | otherwise
  = zip_ty_env tyvars tys emptyVarEnv
zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
zipTyEnv tyvars tys
  | debugIsOn && (length tyvars /= length tys)
  = pprTrace "zipTyEnv" (ppr tyvars $$ ppr tys) emptyVarEnv
  | otherwise
  = zip_ty_env tyvars tys emptyVarEnv
zipTyEnv tyvars tys
  | debugIsOn && (length tyvars /= length tys)
  = pprTrace "zipTyEnv" (ppr tyvars $$ ppr tys) emptyVarEnv
  | otherwise
  = zip_ty_env tyvars tys emptyVarEnv