- -- Applications need a bit of care!
- -- They can match FunTy and TyConApp, so use splitAppTy_maybe
- -- NB: we've already dealt with type variables and Notes,
- -- so if one type is an App the other one jolly well better be too
-unify_ subst (AppTy ty1a ty1b) ty2
- | Just (ty2a, ty2b) <- repSplitAppTy_maybe ty2
- = do { subst' <- unify subst ty1a ty2a
- ; unify subst' ty1b ty2b }
-
-unify_ subst ty1 (AppTy ty2a ty2b)
- | Just (ty1a, ty1b) <- repSplitAppTy_maybe ty1
- = do { subst' <- unify subst ty1a ty2a
- ; unify subst' ty1b ty2b }
-
-unify_ subst ty1 ty2 = failWith (misMatch ty1 ty2)
-
-------------------------------
-unify_pred subst (ClassP c1 tys1) (ClassP c2 tys2)
- | c1 == c2 = unify_tys subst tys1 tys2
-unify_pred subst (IParam n1 t1) (IParam n2 t2)
- | n1 == n2 = unify subst t1 t2
-unify_pred subst p1 p2 = failWith (misMatch (PredTy p1) (PredTy p2))
-
-------------------------------
-unify_tys = unifyList unify
-
-unifyList :: Outputable a
- => (TvSubstEnv -> a -> a -> UM TvSubstEnv)
- -> TvSubstEnv -> [a] -> [a] -> UM TvSubstEnv
-unifyList unifier subst orig_xs orig_ys
- = go subst orig_xs orig_ys
- where
- go subst [] [] = return subst
- go subst (x:xs) (y:ys) = do { subst' <- unifier subst x y
- ; go subst' xs ys }
- go subst _ _ = failWith (lengthMisMatch orig_xs orig_ys)
-
-------------------------------
-uVar :: Bool -- Swapped
- -> TvSubstEnv -- An existing substitution to extend
- -> TyVar -- Type variable to be unified
- -> Type -- with this type
- -> UM TvSubstEnv
-
-uVar swap subst tv1 ty
- = -- Check to see whether tv1 is refined by the substitution
- case (lookupVarEnv subst tv1) of
- -- Yes, call back into unify'
- Just ty' | swap -> unify subst ty ty'
- | otherwise -> unify subst ty' ty
- -- No, continue
- Nothing -> uUnrefined subst tv1 ty ty
-
-
-uUnrefined :: TvSubstEnv -- An existing substitution to extend
- -> TyVar -- Type variable to be unified
- -> Type -- with this type
- -> Type -- (de-noted version)
- -> UM TvSubstEnv
-
--- We know that tv1 isn't refined
-
-uUnrefined subst tv1 ty2 ty2'
- | Just ty2'' <- tcView ty2'
- = uUnrefined subst tv1 ty2 ty2'' -- Unwrap synonyms
- -- This is essential, in case we have
- -- type Foo a = a
- -- and then unify a :=: Foo a
-
-uUnrefined subst tv1 ty2 (TyVarTy tv2)
- | tv1 == tv2 -- Same type variable
- = return subst
-
- -- Check to see whether tv2 is refined
- | Just ty' <- lookupVarEnv subst tv2
- = uUnrefined subst tv1 ty' ty'
-
- -- So both are unrefined; next, see if the kinds force the direction
- | k1 == k2 -- Can update either; so check the bind-flags
- = do { b1 <- tvBindFlag tv1
- ; b2 <- tvBindFlag tv2
- ; case (b1,b2) of
- (BindMe, _) -> bind tv1 ty2
-
- (AvoidMe, BindMe) -> bind tv2 ty1
- (AvoidMe, _) -> bind tv1 ty2
-
- (WildCard, WildCard) -> return subst
- (WildCard, Skolem) -> return subst
- (WildCard, _) -> bind tv2 ty1
-
- (Skolem, WildCard) -> return subst
- (Skolem, Skolem) -> failWith (misMatch ty1 ty2)
- (Skolem, _) -> bind tv2 ty1
- }
-
- | k1 `isSubKind` k2 = bindTv subst tv2 ty1 -- Must update tv2
- | k2 `isSubKind` k1 = bindTv subst tv1 ty2 -- Must update tv1
-
- | otherwise = failWith (kindMisMatch tv1 ty2)
- where
- ty1 = TyVarTy tv1
- k1 = tyVarKind tv1
- k2 = tyVarKind tv2
- bind tv ty = return (extendVarEnv subst tv ty)
-
-uUnrefined subst tv1 ty2 ty2' -- ty2 is not a type variable
- | tv1 `elemVarSet` substTvSet subst (tyVarsOfType ty2')
- = failWith (occursCheck tv1 ty2) -- Occurs check
- | not (k2 `isSubKind` k1)
- = failWith (kindMisMatch tv1 ty2) -- Kind check
- | otherwise
- = bindTv subst tv1 ty2 -- Bind tyvar to the synonym if poss
- where
- k1 = tyVarKind tv1
- k2 = typeKind ty2'
-
-substTvSet :: TvSubstEnv -> TyVarSet -> TyVarSet
--- Apply the non-idempotent substitution to a set of type variables,
--- remembering that the substitution isn't necessarily idempotent
-substTvSet subst tvs
- = foldVarSet (unionVarSet . get) emptyVarSet tvs
- where
- get tv = case lookupVarEnv subst tv of
- Nothing -> unitVarSet tv
- Just ty -> substTvSet subst (tyVarsOfType ty)
-
-bindTv subst tv ty -- ty is not a type variable
- = do { b <- tvBindFlag tv
- ; case b of
- Skolem -> failWith (misMatch (TyVarTy tv) ty)
- WildCard -> return subst
- other -> return (extendVarEnv subst tv ty)
- }
-\end{code}