git.iko.soy/rowtype-yoga/purescript-native
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Don't expand synonyms until after kind checking (#2546)

* Fix #2542. Don't expand synonyms until after kind checking * Missed one * Remove redundant constraint * Make 2542.purs into a warning test * Comment

commit0b9265f60e5c987a9f00edc480e721eb0a8ff88f authorPhil Freeman <paf31@cantab.net> dateMon 9 Jan 2017, 20:38 (10 years ago) parent52ee527
3 files changed+33−5
compare with golang
unifiedsplit
examples/failing/2542.purs+9 examples/warning/2542.purs+16 src/Language/PureScript/TypeChecker/Types.hs+8−5
examples/failing/2542.pursnew file+9
@@ -0,0 +1,9 @@
1+-- @shouldFailWith UndefinedTypeVariable
2+module Main where
3+
4+type T = forall a. Array a
5+
6+foo :: T
7+foo = bar where
8+ bar :: Array a
9+ bar = []
examples/warning/2542.pursnew file+16
@@ -0,0 +1,16 @@
1+-- @shouldWarnWith MissingTypeDeclaration
2+module Main where
3+
4+import Control.Monad.Eff.Console
5+
6+type T = forall a. Array a
7+
8+-- | Note: This should not raise a `ShadowedTypeVar` warning as the
9+-- | type `a` introduced in `T` should not be in scope
10+-- | in the definition of `bar`.
11+foo :: T
12+foo = bar where
13+ bar :: forall a. Array a
14+ bar = []
15+
16+main = log "Done"
src/Language/PureScript/TypeChecker/Types.hs+8−5
@@ -187,7 +187,7 @@ data SplitBindingGroup = SplitBindingGroup
187187-- This function also generates fresh unification variables for the types of
188188-- declarations without type annotations, returned in the 'UntypedData' structure.
189189typeDictionaryForBindingGroup
190− :: (MonadState CheckState m, MonadError MultipleErrors m, MonadWriter MultipleErrors m)
190+ :: (MonadState CheckState m, MonadWriter MultipleErrors m)
191191 => Maybe ModuleName
192192 -> [(Ident, Expr)]
193193 -> m SplitBindingGroup
@@ -197,7 +197,7 @@ typeDictionaryForBindingGroup moduleName vals = do
197197 -- fully expanded types.
198198 let (untyped, typed) = partitionEithers (map splitTypeAnnotation vals)
199199 (typedDict, typed') <- fmap unzip . for typed $ \(ident, (expr, ty, checkType)) -> do
200− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< replaceTypeWildcards $ ty
200+ ty' <- replaceTypeWildcards ty
201201 return ((ident, ty'), (ident, (expr, ty', checkType)))
202202 -- Create fresh unification variables for the types of untyped declarations
203203 (untypedDict, untyped') <- fmap unzip . for untyped $ \(ident, expr) -> do
@@ -233,11 +233,14 @@ checkTypedBindingGroupElement mn (ident, (val, ty, checkType)) dict = do
233233 -- Kind check
234234 (kind, args) <- kindOfWithScopedVars ty
235235 checkTypeKind ty kind
236+ -- We replace type synonyms _after_ kind-checking, since we don't want type
237+ -- synonym expansion to bring type variables into scope. See #2542.
238+ ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
236239 -- Check the type with the new names in scope
237240 val' <- if checkType
238− then withScopedTypeVars mn args $ bindNames dict $ TypedValue True <$> check val ty <*> pure ty
239− else return (TypedValue False val ty)
240− return (ident, (val', ty))
241+ then withScopedTypeVars mn args $ bindNames dict $ TypedValue True <$> check val ty' <*> pure ty'
242+ else return (TypedValue False val ty')
243+ return (ident, (val', ty'))
241244
242245-- | Infer a type for a value in a binding group which lacks an annotation.
243246typeForBindingGroupElement