--- NB: we *cannot* short-cut the newtype comparison thus:
--- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
--- | (tc1 == tc2) = (eq_tys env tys1 tys2)
---
--- Consider:
--- newtype T a = MkT [a]
--- newtype Foo m = MkFoo (forall a. m a -> Int)
--- w1 :: Foo []
--- w1 = ...
---
--- w2 :: Foo T
--- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
---
--- We end up with w2 = w1; so we need that Foo T = Foo []
--- but we can only expand saturated newtypes, so just comparing
--- T with [] won't do.
-
-eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
-eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
-
--- The rest is plain sailing
-eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
- Just tv1a -> tv1a == tv2
- Nothing -> tv1 == tv2
-eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
- | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
- | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
-eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
-eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
-eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
-eq_ty env t1 t2 = False
-
-eq_tys env [] [] = True
-eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
-eq_tys env tys1 tys2 = False
+tcCmpTypes :: [Type] -> [Type] -> Ordering
+tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
+
+tcEqPred :: PredType -> PredType -> Bool
+tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
+
+tcCmpPred :: PredType -> PredType -> Ordering
+tcCmpPred p1 p2 = cmpPred p1 p2
+
+tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
+tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
+\end{code}
+
+Now here comes the real worker
+
+\begin{code}
+cmpType :: Type -> Type -> Ordering
+cmpType t1 t2 = cmpTypeX rn_env t1 t2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
+
+cmpTypes :: [Type] -> [Type] -> Ordering
+cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
+
+cmpPred :: PredType -> PredType -> Ordering
+cmpPred p1 p2 = cmpPredX rn_env p1 p2
+ where
+ rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
+
+cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
+cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
+ | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
+
+cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
+cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
+cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
+cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
+cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
+cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
+cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
+
+ -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
+cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
+
+cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
+cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
+
+cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
+cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
+cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
+
+cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
+cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
+cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
+
+cmpTypeX env (PredTy _) t2 = GT
+
+cmpTypeX env _ _ = LT
+
+-------------
+cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
+cmpTypesX env [] [] = EQ
+cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
+cmpTypesX env [] tys = LT
+cmpTypesX env ty [] = GT
+
+-------------
+cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
+cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
+ -- Compare types as well as names for implicit parameters
+ -- This comparison is used exclusively (I think) for the
+ -- finite map built in TcSimplify
+cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2
+cmpPredX env (IParam _ _) (ClassP _ _) = LT
+cmpPredX env (ClassP _ _) (IParam _ _) = GT
+\end{code}
+
+PredTypes are used as a FM key in TcSimplify,
+so we take the easy path and make them an instance of Ord
+
+\begin{code}
+instance Eq PredType where { (==) = tcEqPred }
+instance Ord PredType where { compare = tcCmpPred }