git.iko.soy/elk
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elk/compiler/Type/Unify.hs
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1{-# OPTIONS_GHC -W #-}
2module Type.Unify (unify) where
4import Control.Monad.State
5import qualified Data.Map as Map
6import qualified Data.Maybe as Maybe
7import qualified Data.UnionFind.IO as UF
8import qualified AST.Annotation as A
9import qualified Type.State as TS
10import Type.Type
11import Type.PrettyPrint
12import Text.PrettyPrint (render)
14unify :: A.Region -> Variable -> Variable -> StateT TS.SolverState IO ()
15unify region variable1 variable2 = do
16 equivalent <- liftIO $ UF.equivalent variable1 variable2
17 if equivalent then return ()
18 else actuallyUnify region variable1 variable2
20actuallyUnify :: A.Region -> Variable -> Variable -> StateT TS.SolverState IO ()
21actuallyUnify region variable1 variable2 = do
22 desc1 <- liftIO $ UF.descriptor variable1
23 desc2 <- liftIO $ UF.descriptor variable2
24 let unify' = unify region
26 name' :: Maybe String
27 name' = case (name desc1, name desc2) of
28 (Just name1, Just name2) ->
29 case (flex desc1, flex desc2) of
30 (_, Flexible) -> Just name1
31 (Flexible, _) -> Just name2
32 (Is Number, Is _) -> Just name1
33 (Is _, Is Number) -> Just name2
34 (Is _, Is _) -> Just name1
35 (_, _) -> Nothing
36 (Just name1, _) -> Just name1
37 (_, Just name2) -> Just name2
38 _ -> Nothing
40 flex' :: Flex
41 flex' = case (flex desc1, flex desc2) of
42 (f, Flexible) -> f
43 (Flexible, f) -> f
44 (Is Number, Is _) -> Is Number
45 (Is _, Is Number) -> Is Number
46 (Is super, Is _) -> Is super
47 (_, _) -> Flexible
49 rank' :: Int
50 rank' = min (rank desc1) (rank desc2)
52 merge1 :: StateT TS.SolverState IO ()
53 merge1 = liftIO $ do
54 if rank desc1 < rank desc2 then UF.union variable2 variable1
55 else UF.union variable1 variable2
56 UF.modifyDescriptor variable1 $ \desc ->
57 desc { structure = structure desc1, flex = flex', name = name' }
59 merge2 :: StateT TS.SolverState IO ()
60 merge2 = liftIO $ do
61 if rank desc1 < rank desc2 then UF.union variable2 variable1
62 else UF.union variable1 variable2
63 UF.modifyDescriptor variable2 $ \desc ->
64 desc { structure = structure desc2, flex = flex', name = name' }
66 merge = if rank desc1 < rank desc2 then merge1 else merge2
68 fresh :: Maybe (Term1 Variable) -> StateT TS.SolverState IO Variable
69 fresh structure = do
70 var <- liftIO . UF.fresh $ Descriptor {
71 structure = structure, rank = rank', flex = flex',
72 name = name', copy = Nothing, mark = noMark
73 }
74 TS.register var
76 flexAndUnify var = do
77 liftIO $ UF.modifyDescriptor var $ \desc -> desc { flex = Flexible }
78 unify' variable1 variable2
80 unifyNumber svar name
81 | name `elem` ["Int","Float","number"] = flexAndUnify svar
82 | otherwise = TS.addError region (Just hint) variable1 variable2
83 where hint = "A number must be an Int or Float."
85 comparableError maybe =
86 TS.addError region (Just $ Maybe.fromMaybe msg maybe) variable1 variable2
87 where msg = "A comparable must be an Int, Float, Char, String, list, or tuple."
89 unifyComparable var name
90 | name `elem` ["Int","Float","Char","String","comparable"] = flexAndUnify var
91 | otherwise = comparableError Nothing
93 unifyComparableStructure varSuper varFlex =
94 do struct <- liftIO $ collectApps varFlex
95 case struct of
96 Other -> comparableError Nothing
97 List v -> do flexAndUnify varSuper
98 unify' v =<< liftIO (var $ Is Comparable)
99 Tuple vs
100 | length vs > 6 ->
101 comparableError $ Just "Cannot compare a tuple with more than 6 elements."
102 | otherwise ->
103 do flexAndUnify varSuper
104 cmpVars <- liftIO $ forM [1..length vs] $ \_ -> var (Is Comparable)
105 zipWithM_ unify' vs cmpVars
107 unifyAppendable varSuper varFlex =
108 do struct <- liftIO $ collectApps varFlex
109 case struct of
110 List _ -> flexAndUnify varSuper
111 _ -> comparableError Nothing
113 rigidError variable = TS.addError region (Just hint) variable1 variable2
114 where
115 var = "'" ++ render (pretty Never variable) ++ "'"
116 hint = "Cannot unify rigid type variable " ++ var ++
117 ".\nThe problem probably relates to a type annotation. Note that rigid type\n\
118 \variables are not shared between a top-level and let-bound type annotations."
120 superUnify =
121 case (flex desc1, flex desc2, name desc1, name desc2) of
122 (Is super1, Is super2, _, _)
123 | super1 == super2 -> merge
124 (Is Number, Is Comparable, _, _) -> merge1
125 (Is Comparable, Is Number, _, _) -> merge2
127 (Is Number, _, _, Just name) -> unifyNumber variable1 name
128 (_, Is Number, Just name, _) -> unifyNumber variable2 name
130 (Is Comparable, _, _, Just name) -> unifyComparable variable1 name
131 (_, Is Comparable, Just name, _) -> unifyComparable variable2 name
132 (Is Comparable, _, _, _) -> unifyComparableStructure variable1 variable2
133 (_, Is Comparable, _, _) -> unifyComparableStructure variable2 variable1
135 (Is Appendable, _, _, Just ctor)
136 | ctor `elem` ["Text.Text","String"] -> flexAndUnify variable1
137 (_, Is Appendable, Just ctor, _)
138 | ctor `elem` ["Text.Text","String"] -> flexAndUnify variable2
139 (Is Appendable, _, _, _) -> unifyAppendable variable1 variable2
140 (_, Is Appendable, _, _) -> unifyAppendable variable2 variable1
142 (Rigid, _, _, _) -> rigidError variable1
143 (_, Rigid, _, _) -> rigidError variable2
144 _ -> TS.addError region Nothing variable1 variable2
146 case (structure desc1, structure desc2) of
147 (Nothing, Nothing) | flex desc1 == Flexible && flex desc1 == Flexible -> merge
148 (Nothing, _) | flex desc1 == Flexible -> merge2
149 (_, Nothing) | flex desc2 == Flexible -> merge1
151 (Just (Var1 v), _) -> unify' v variable2
152 (_, Just (Var1 v)) -> unify' v variable1
154 (Nothing, _) -> superUnify
155 (_, Nothing) -> superUnify
157 (Just type1, Just type2) ->
158 case (type1,type2) of
159 (App1 term1 term2, App1 term1' term2') ->
160 do merge
161 unify' term1 term1'
162 unify' term2 term2'
163 (Fun1 term1 term2, Fun1 term1' term2') ->
164 do merge
165 unify' term1 term1'
166 unify' term2 term2'
168 (EmptyRecord1, EmptyRecord1) ->
169 return ()
171 (Record1 fields ext, EmptyRecord1) | Map.null fields -> unify' ext variable2
172 (EmptyRecord1, Record1 fields ext) | Map.null fields -> unify' ext variable1
174 (Record1 fields1 ext1, Record1 fields2 ext2) ->
175 do sequence . concat . Map.elems $ Map.intersectionWith (zipWith unify') fields1 fields2
176 let mkRecord fs ext = fresh . Just $ Record1 fs ext
177 case (Map.null fields1', Map.null fields2') of
178 (True , True ) -> unify' ext1 ext2
179 (True , False) -> do
180 record2' <- mkRecord fields2' ext2
181 unify' ext1 record2'
182 (False, True ) -> do
183 record1' <- mkRecord fields1' ext1
184 unify' record1' ext2
185 (False, False) -> do
186 record1' <- mkRecord fields1' =<< fresh Nothing
187 record2' <- mkRecord fields2' =<< fresh Nothing
188 unify' record1' ext2
189 unify' ext1 record2'
190 where
191 fields1' = unmerged fields1 fields2
192 fields2' = unmerged fields2 fields1
194 unmerged a b = Map.filter (not . null) $ Map.union (Map.intersectionWith eat a b) a
196 eat (_:xs) (_:ys) = eat xs ys
197 eat xs _ = xs
199 _ -> TS.addError region Nothing variable1 variable2