480b297 · rowtype-yoga/purescript-native

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

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Fix #620. More rigorous overlap check.

480b297Phil Freeman12 years ago

examples/failing/OverlappingInstances.pursnew file+11

compare with golang

unifiedsplit

@@ -0,0 +1,11 @@

1+module OverlappingInstances where

3+data A = A

5+instance showA1 :: Show A where

6+ show A = "Instance 1"

8+instance showA2 :: Show A where

9+ show A = "Instance 2"

10+

11+main = Debug.Trace.trace $ show A

src/Language/PureScript/TypeChecker/Types.hs+18−10

@@ -376,16 +376,18 @@ entails env moduleName context = solve (sortedNubBy canonicalizeDictionary (filt

376 --

377 checkOverlaps :: [DictionaryValue] -> Check Expr

378 checkOverlaps dicts =

379− case sortedNubBy dictTrace (chooseSimplestDictionaries dicts) of

379+ case [ (d1, d2) | d1 <- dicts, d2 <- dicts, d1 `overlapping` d2 ] of

380− [] -> throwError . strMsg $ "No instance found for " ++ show className ++ " " ++ unwords (map prettyPrintTypeAtom tys)

381− [_] -> return $ dictionaryValueToValue $ head dicts

382− (d1 : d2 : _) -> throwError . strMsg $ unlines

380+ (d1, d2) : _ -> throwError . strMsg $ unlines

383 [ "Overlapping instances found for " ++ show className ++ " " ++ unwords (map prettyPrintType tys) ++ "."

381 [ "Overlapping instances found for " ++ show className ++ " " ++ unwords (map prettyPrintType tys) ++ "."

384 , "For example:"

382 , "For example:"

385 , prettyPrintDictionaryValue d1

383 , prettyPrintDictionaryValue d1

386 , "and:"

384 , "and:"

387 , prettyPrintDictionaryValue d2

385 , prettyPrintDictionaryValue d2

388 ]

386 ]

387+ _ -> case chooseSimplestDictionaries dicts of

388+ [] -> throwError . strMsg $

389+ "No instance found for " ++ show className ++ " " ++ unwords (map prettyPrintTypeAtom tys)

390+ d : _ -> return $ dictionaryValueToValue d

389 -- Choose the simplest DictionaryValues from a list of candidates

391 -- Choose the simplest DictionaryValues from a list of candidates

390 -- The reason for this function is as follows:

392 -- The reason for this function is as follows:

391 -- When considering overlapping instances, we don't want to consider the same dictionary

393 -- When considering overlapping instances, we don't want to consider the same dictionary

@@ -402,13 +404,19 @@ entails env moduleName context = solve (sortedNubBy canonicalizeDictionary (filt

402 isSimpleDictionaryValue (DependentDictionaryValue _ ds) = all isSimpleDictionaryValue ds

404 isSimpleDictionaryValue (DependentDictionaryValue _ ds) = all isSimpleDictionaryValue ds

403 isSimpleDictionaryValue _ = True

405 isSimpleDictionaryValue _ = True

404 -- |

406 -- |

405− -- Get the "trace" of a DictionaryValue - that is, remove all SubclassDictionaryValue

407+ -- Check if two dictionaries are overlapping

406− -- data constructors

408+ --

409+ -- Dictionaries which are subclass dictionaries cannot overlap, since otherwise the overlap would have

410+ -- been caught when constructing superclass dictionaries.

407 --

411 --

408− dictTrace :: DictionaryValue -> DictionaryValue

412+ overlapping :: DictionaryValue -> DictionaryValue -> Bool

409− dictTrace (DependentDictionaryValue fnName dicts) = DependentDictionaryValue fnName $ map dictTrace dicts

413+ overlapping (LocalDictionaryValue nm1) (LocalDictionaryValue nm2) | nm1 == nm2 = False

414+ overlapping (GlobalDictionaryValue nm1) (GlobalDictionaryValue nm2) | nm1 == nm2 = False

415+ overlapping (DependentDictionaryValue nm1 ds1) (DependentDictionaryValue nm2 ds2)

416+ | nm1 == nm2 = any id $ zipWith overlapping ds1 ds2

410− dictTrace (SubclassDictionaryValue dict _ _) = dictTrace dict

417+ overlapping (SubclassDictionaryValue _ _ _) _ = False

411− dictTrace other = other

418+ overlapping _ (SubclassDictionaryValue _ _ _) = False

419+ overlapping _ _ = True

412 -- |

420 -- |

413 -- Render a DictionaryValue fit for human consumption in error messages

421 -- Render a DictionaryValue fit for human consumption in error messages

414 --

422 --