8f26b7d · rowtype-yoga/purescript-native

git.iko.soy/rowtype-yoga/purescript-native

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Fix #600

8f26b7dPhil Freeman12 years ago

examples/passing/IfThenElseMaybe.pursnew file+7

@@ -0,0 +1,7 @@

1+module Main where

3+data Maybe a = Nothing | Just a

5+test = if true then Just 10 else Nothing

7+main = Debug.Trace.trace "Done"

src/Language/PureScript/TypeChecker/Types.hs+14−2

@@ -655,8 +655,8 @@ infer' (IfThenElse cond th el) = do

655 cond' <- check cond tyBoolean

656 v2@(TypedValue _ _ t2) <- infer th

657 v3@(TypedValue _ _ t3) <- infer el

658− t2 =?= t3

658+ (v2', v3', t) <- meet v2 v3 t2 t3

659− return $ TypedValue True (IfThenElse cond' v2 v3) t2

659+ return $ TypedValue True (IfThenElse cond' v2' v3') t

660infer' (Let ds val) = do

661 (ds', val'@(TypedValue _ _ valTy)) <- inferLetBinding [] ds val infer

662 return $ TypedValue True (Let ds' val') valTy

@@ -1119,6 +1119,18 @@ subsumes' val ty1 ty2 = do

1119 ty1 =?= ty2

1120 return val

1121

1122+-- |

1123+-- Compute the meet of two types, i.e. the most general type which both types subsume.

1124+-- TODO: handle constrained types

1125+--

1126+meet :: Expr -> Expr -> Type -> Type -> UnifyT Type Check (Expr, Expr, Type)

1127+meet e1 e2 t1@(ForAll _ _ _) t2 = meet e1 e2 t1 t2

1128+meet e1 e2 t1 (ForAll ident t2 _) = do

1129+ t2' <- replaceVarWithUnknown ident t2

1130+ meet e1 e2 t1 t2'

1131+meet e1 e2 t1 t2 = do

1132+ t1 =?= t2

1133+ return (e1, e2, t1)

1122

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1123

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