diff --git a/examples/failing/TypeSynonyms4.purs b/examples/failing/TypeSynonyms4.purs
new file mode 100644
--- /dev/null
+++ b/examples/failing/TypeSynonyms4.purs
@@ -0,0 +1,8 @@
+module TypeSynonyms4 where
+
+type F x y = x -> y
+
+type G x = F x
+
+f :: G String String -> String
+f k = k "Done"
diff --git a/purescript.cabal b/purescript.cabal
--- a/purescript.cabal
+++ b/purescript.cabal
@@ -1,5 +1,5 @@
 name: purescript
-version: 0.6.1.1
+version: 0.6.1.2
 cabal-version: >=1.8
 build-type: Simple
 license: MIT
diff --git a/src/Language/PureScript/AST/Binders.hs b/src/Language/PureScript/AST/Binders.hs
--- a/src/Language/PureScript/AST/Binders.hs
+++ b/src/Language/PureScript/AST/Binders.hs
@@ -68,7 +68,7 @@
   -- |
   -- A binder with source position information
   --
-  | PositionedBinder SourcePos Binder deriving (Show, D.Data, D.Typeable)
+  | PositionedBinder SourceSpan Binder deriving (Show, D.Data, D.Typeable)
 
 -- |
 -- Collect all names introduced in binders in an expression
diff --git a/src/Language/PureScript/AST/Declarations.hs b/src/Language/PureScript/AST/Declarations.hs
--- a/src/Language/PureScript/AST/Declarations.hs
+++ b/src/Language/PureScript/AST/Declarations.hs
@@ -57,7 +57,7 @@
   -- |
   -- A declaration reference with source position information
   --
-  | PositionedDeclarationRef SourcePos DeclarationRef
+  | PositionedDeclarationRef SourceSpan DeclarationRef
   deriving (Show, D.Data, D.Typeable)
 
 instance Eq DeclarationRef where
@@ -147,7 +147,7 @@
   -- |
   -- A declaration with source position information
   --
-  | PositionedDeclaration SourcePos Declaration
+  | PositionedDeclaration SourceSpan Declaration
   deriving (Show, D.Data, D.Typeable)
 
 -- |
@@ -324,7 +324,7 @@
   -- |
   -- A value with source position information
   --
-  | PositionedValue SourcePos Expr deriving (Show, D.Data, D.Typeable)
+  | PositionedValue SourceSpan Expr deriving (Show, D.Data, D.Typeable)
 
 -- |
 -- An alternative in a case statement
@@ -359,4 +359,4 @@
   -- |
   -- A do notation element with source position information
   --
-  | PositionedDoNotationElement SourcePos DoNotationElement deriving (Show, D.Data, D.Typeable)
+  | PositionedDoNotationElement SourceSpan DoNotationElement deriving (Show, D.Data, D.Typeable)
diff --git a/src/Language/PureScript/AST/SourcePos.hs b/src/Language/PureScript/AST/SourcePos.hs
--- a/src/Language/PureScript/AST/SourcePos.hs
+++ b/src/Language/PureScript/AST/SourcePos.hs
@@ -23,13 +23,9 @@
 --
 data SourcePos = SourcePos
   { -- |
-    -- Source name
-    --
-    sourceName :: String
-    -- |
     -- Line number
     --
-  , sourcePosLine :: Int
+    sourcePosLine :: Int
     -- |
     -- Column number
     --
@@ -37,4 +33,21 @@
   } deriving (D.Data, D.Typeable)
 
 instance Show SourcePos where
-  show sp = sourceName sp ++ " line " ++ show (sourcePosLine sp) ++ ", column " ++ show (sourcePosColumn sp)
+  show sp = "line " ++ show (sourcePosLine sp) ++ ", column " ++ show (sourcePosColumn sp)
+
+data SourceSpan = SourceSpan
+  { -- |
+    -- Source name
+    --
+    spanName :: String
+    -- |
+    -- Start of the span
+    --
+  , spanStart :: SourcePos
+    -- End of the span
+    --
+  , spanEnd :: SourcePos
+  } deriving (D.Data, D.Typeable)
+  
+instance Show SourceSpan where
+  show sp = spanName sp ++ " " ++ show (spanStart sp) ++ " - " ++ show (spanEnd sp)
diff --git a/src/Language/PureScript/CodeGen/Externs.hs b/src/Language/PureScript/CodeGen/Externs.hs
--- a/src/Language/PureScript/CodeGen/Externs.hs
+++ b/src/Language/PureScript/CodeGen/Externs.hs
@@ -97,7 +97,7 @@
 
     exportToPs (TypeInstanceRef ident) = do
       let TypeClassDictionaryInScope { tcdClassName = className, tcdInstanceTypes = tys, tcdDependencies = deps} =
-            fromMaybe (error $ "Type class instance has no dictionary in exportToPs") . find ((== Qualified (Just moduleName) ident) . tcdName) $ M.elems $ typeClassDictionaries env
+            fromMaybe (error $ "Type class instance has no dictionary in exportToPs") . find (\tcd -> tcdName tcd == Qualified (Just moduleName) ident && tcdType tcd == TCDRegular) $ M.elems $ typeClassDictionaries env
       let constraintsText = case fromMaybe [] deps of
                               [] -> ""
                               cs -> "(" ++ intercalate ", " (map (\(pn, tys') -> show pn ++ " " ++ unwords (map prettyPrintTypeAtom tys')) cs) ++ ") => "
diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -56,7 +56,7 @@
         -- |
         -- Optional source position information
         --
-      , compileErrorPosition :: Maybe SourcePos
+      , compileErrorPosition :: Maybe SourceSpan
       }
   deriving (Show)
 
@@ -109,7 +109,7 @@
 mkErrorStack :: String -> Maybe ErrorSource -> ErrorStack
 mkErrorStack msg t = ErrorStack [CompileError msg t Nothing]
 
-positionError :: SourcePos -> ErrorStack
+positionError :: SourceSpan -> ErrorStack
 positionError pos = ErrorStack [CompileError "" Nothing (Just pos)]
 
 -- |
@@ -121,7 +121,7 @@
 -- |
 -- Rethrow an error with source position information
 --
-rethrowWithPosition :: (MonadError ErrorStack m) => SourcePos -> m a -> m a
+rethrowWithPosition :: (MonadError ErrorStack m) => SourceSpan -> m a -> m a
 rethrowWithPosition pos = rethrow (positionError pos <>)
 
 -- |
diff --git a/src/Language/PureScript/Parser/Declarations.hs b/src/Language/PureScript/Parser/Declarations.hs
--- a/src/Language/PureScript/Parser/Declarations.hs
+++ b/src/Language/PureScript/Parser/Declarations.hs
@@ -48,10 +48,15 @@
 -- |
 -- Read source position information
 --
-sourcePos :: P.Parsec s u SourcePos
-sourcePos = toSourcePos <$> P.getPosition
+withSourceSpan :: (SourceSpan -> a -> a) -> P.Parsec s u a -> P.Parsec s u a
+withSourceSpan f p = do
+  start <- P.getPosition
+  x <- p
+  end <- P.getPosition
+  let sp = SourceSpan (P.sourceName start) (toSourcePos start) (toSourcePos end)
+  return $ f sp x
   where
-  toSourcePos p = SourcePos (P.sourceName p) (P.sourceLine p) (P.sourceColumn p)
+  toSourcePos pos = SourcePos (P.sourceLine pos) (P.sourceColumn pos)
 
 kindedIdent :: P.Parsec String ParseState (String, Maybe Kind)
 kindedIdent = (, Nothing) <$> identifier
@@ -165,11 +170,11 @@
 
 
 parseDeclarationRef :: P.Parsec String ParseState DeclarationRef
-parseDeclarationRef = PositionedDeclarationRef <$> sourcePos <*>
-  (ValueRef <$> parseIdent
-   <|> do name <- properName
-          dctors <- P.optionMaybe $ parens (lexeme (P.string "..") *> pure Nothing <|> Just <$> commaSep properName)
-          return $ maybe (TypeClassRef name) (TypeRef name) dctors)
+parseDeclarationRef = withSourceSpan PositionedDeclarationRef $
+  ValueRef <$> parseIdent
+    <|> do name <- properName
+           dctors <- P.optionMaybe $ parens (lexeme (P.string "..") *> pure Nothing <|> Just <$> commaSep properName)
+           return $ maybe (TypeClassRef name) (TypeRef name) dctors
 
 parseTypeClassDeclaration :: P.Parsec String ParseState Declaration
 parseTypeClassDeclaration = do
@@ -203,7 +208,7 @@
   return $ TypeInstanceDeclaration name (fromMaybe [] deps) className ty members
 
 positioned :: P.Parsec String ParseState Declaration -> P.Parsec String ParseState Declaration
-positioned d = PositionedDeclaration <$> sourcePos <*> d
+positioned d = withSourceSpan PositionedDeclaration d
 
 -- |
 -- Parse a single declaration
@@ -222,10 +227,10 @@
                    ]) P.<?> "declaration"
 
 parseLocalDeclaration :: P.Parsec String ParseState Declaration
-parseLocalDeclaration = PositionedDeclaration <$> sourcePos <*> P.choice
+parseLocalDeclaration = positioned (P.choice
                    [ parseTypeDeclaration
                    , parseValueDeclaration
-                   ] P.<?> "local declaration"
+                   ] P.<?> "local declaration")
 
 -- |
 -- Parse a module header and a collection of declarations
@@ -374,10 +379,10 @@
 -- Parse a value
 --
 parseValue :: P.Parsec String ParseState Expr
-parseValue = PositionedValue <$> sourcePos <*>
+parseValue = withSourceSpan PositionedValue
   (P.buildExpressionParser operators
-   . C.buildPostfixParser postfixTable2
-   $ indexersAndAccessors) P.<?> "expression"
+    . C.buildPostfixParser postfixTable2
+    $ indexersAndAccessors) P.<?> "expression"
   where
   indexersAndAccessors = C.buildPostfixParser postfixTable1 parseValueAtom
   postfixTable1 = [ parseAccessor
@@ -439,8 +444,7 @@
 -- Parse a binder
 --
 parseBinder :: P.Parsec String ParseState Binder
-parseBinder = PositionedBinder <$> sourcePos <*>
-    P.buildExpressionParser operators parseBinderAtom P.<?> "expression"
+parseBinder = withSourceSpan PositionedBinder (P.buildExpressionParser operators parseBinderAtom P.<?> "expression")
   where
   operators = [ [ P.Infix ( C.lexeme (P.try $ C.indented *> C.reservedOp ":") >> return ConsBinder) P.AssocRight ] ]
   parseBinderAtom :: P.Parsec String ParseState Binder
diff --git a/src/Language/PureScript/Sugar/Names.hs b/src/Language/PureScript/Sugar/Names.hs
--- a/src/Language/PureScript/Sugar/Names.hs
+++ b/src/Language/PureScript/Sugar/Names.hs
@@ -198,7 +198,7 @@
   where
   (go, _, _, _, _) = everywhereWithContextOnValuesM (Nothing, []) updateDecl updateValue updateBinder updateCase defS
 
-  updateDecl :: (Maybe SourcePos, [Ident]) -> Declaration -> Either ErrorStack ((Maybe SourcePos, [Ident]), Declaration)
+  updateDecl :: (Maybe SourceSpan, [Ident]) -> Declaration -> Either ErrorStack ((Maybe SourceSpan, [Ident]), Declaration)
   updateDecl (_, bound) d@(PositionedDeclaration pos _) = return ((Just pos, bound), d)
   updateDecl (pos, bound) (DataDeclaration dtype name args dctors) =
     (,) (pos, bound) <$> (DataDeclaration dtype name args <$> mapM (sndM (mapM (updateTypesEverywhere pos))) dctors)
@@ -216,7 +216,7 @@
     (,) (pos, name : bound) <$> (ExternDeclaration fit name js <$> updateTypesEverywhere pos ty)
   updateDecl s d = return (s, d)
 
-  updateValue :: (Maybe SourcePos, [Ident]) -> Expr -> Either ErrorStack ((Maybe SourcePos, [Ident]), Expr)
+  updateValue :: (Maybe SourceSpan, [Ident]) -> Expr -> Either ErrorStack ((Maybe SourceSpan, [Ident]), Expr)
   updateValue (_, bound) v@(PositionedValue pos' _) = return ((Just pos', bound), v)
   updateValue (pos, bound) (Abs (Left arg) val') = return ((pos, arg : bound), Abs (Left arg) val')
   updateValue (pos, bound) (Let ds val') =
@@ -234,12 +234,12 @@
   updateValue s@(pos, _) (TypedValue check val ty) = (,) s <$> (TypedValue check val <$> updateTypesEverywhere pos ty)
   updateValue s v = return (s, v)
 
-  updateBinder :: (Maybe SourcePos, [Ident]) -> Binder -> Either ErrorStack ((Maybe SourcePos, [Ident]), Binder)
+  updateBinder :: (Maybe SourceSpan, [Ident]) -> Binder -> Either ErrorStack ((Maybe SourceSpan, [Ident]), Binder)
   updateBinder (_, bound) v@(PositionedBinder pos _) = return ((Just pos, bound), v)
   updateBinder s@(pos, _) (ConstructorBinder name b) = (,) s <$> (ConstructorBinder <$> updateDataConstructorName name pos <*> pure b)
   updateBinder s v = return (s, v)
 
-  updateCase :: (Maybe SourcePos, [Ident]) -> CaseAlternative -> Either ErrorStack ((Maybe SourcePos, [Ident]), CaseAlternative)
+  updateCase :: (Maybe SourceSpan, [Ident]) -> CaseAlternative -> Either ErrorStack ((Maybe SourceSpan, [Ident]), CaseAlternative)
   updateCase (pos, bound) c@(CaseAlternative bs _) = return ((pos, concatMap binderNames bs ++ bound), c)
 
   letBoundVariable :: Declaration -> Maybe Ident
@@ -247,10 +247,10 @@
   letBoundVariable (PositionedDeclaration _ d) = letBoundVariable d
   letBoundVariable _ = Nothing
 
-  updateTypesEverywhere :: Maybe SourcePos -> Type -> Either ErrorStack Type
+  updateTypesEverywhere :: Maybe SourceSpan -> Type -> Either ErrorStack Type
   updateTypesEverywhere pos0 = everywhereOnTypesM (updateType pos0)
     where
-    updateType :: Maybe SourcePos -> Type -> Either ErrorStack Type
+    updateType :: Maybe SourceSpan -> Type -> Either ErrorStack Type
     updateType pos (TypeConstructor name) = TypeConstructor <$> updateTypeName name pos
     updateType pos (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym <$> updateTypeName name pos <*> pure tys
     updateType pos (ConstrainedType cs t) = ConstrainedType <$> updateConstraints pos cs <*> pure t
@@ -269,7 +269,7 @@
                             -> (ImportEnvironment -> M.Map (Qualified a) (Qualified a))
                             -> (Exports -> a -> Bool)
                             -> Qualified a
-                            -> Maybe SourcePos
+                            -> Maybe SourceSpan
                             -> Either ErrorStack (Qualified a)
   update t getI checkE qname@(Qualified mn' name) pos = positioned $ case (M.lookup qname imports', mn') of
     (Just qname', _) -> return qname'
@@ -385,7 +385,7 @@
 -- Finds the imports within a module, mapping the imported module name to an optional set of
 -- explicitly imported declarations.
 --
-findImports :: [Declaration] -> M.Map ModuleName (Maybe SourcePos, ImportDeclarationType, Maybe ModuleName)
+findImports :: [Declaration] -> M.Map ModuleName (Maybe SourceSpan, ImportDeclarationType, Maybe ModuleName)
 findImports = foldl (findImports' Nothing) M.empty
   where
   findImports' pos result (ImportDeclaration mn typ qual) = M.insert mn (pos, typ, qual) result
@@ -403,10 +403,10 @@
   -- A Map from module name to the source position for the import, the list of imports from that
   -- module (where Nothing indicates everything is to be imported), and optionally a qualified name
   -- for the module
-  scope :: M.Map ModuleName (Maybe SourcePos, ImportDeclarationType, Maybe ModuleName)
+  scope :: M.Map ModuleName (Maybe SourceSpan, ImportDeclarationType, Maybe ModuleName)
   scope = M.insert currentModule (Nothing, Unqualified, Nothing) (findImports decls)
 
-  resolveImport' :: ImportEnvironment -> (ModuleName, (Maybe SourcePos, ImportDeclarationType, Maybe ModuleName)) -> Either ErrorStack ImportEnvironment
+  resolveImport' :: ImportEnvironment -> (ModuleName, (Maybe SourceSpan, ImportDeclarationType, Maybe ModuleName)) -> Either ErrorStack ImportEnvironment
   resolveImport' imp (mn, (pos, typ, impQual)) = do
     modExports <- positioned $ maybe (throwError $ mkErrorStack ("Cannot import unknown module '" ++ show mn ++ "'") Nothing) return $ mn `M.lookup` env
     positioned $ resolveImport currentModule mn modExports imp impQual typ
diff --git a/src/Language/PureScript/Sugar/Operators.hs b/src/Language/PureScript/Sugar/Operators.hs
--- a/src/Language/PureScript/Sugar/Operators.hs
+++ b/src/Language/PureScript/Sugar/Operators.hs
@@ -76,15 +76,15 @@
   go (Parens val) = val
   go val = val
 
-collectFixities :: Module -> [(Qualified Ident, SourcePos, Fixity)]
+collectFixities :: Module -> [(Qualified Ident, SourceSpan, Fixity)]
 collectFixities (Module moduleName ds _) = concatMap collect ds
   where
-  collect :: Declaration -> [(Qualified Ident, SourcePos, Fixity)]
+  collect :: Declaration -> [(Qualified Ident, SourceSpan, Fixity)]
   collect (PositionedDeclaration pos (FixityDeclaration fixity name)) = [(Qualified (Just moduleName) (Op name), pos, fixity)]
   collect FixityDeclaration{} = error "Fixity without srcpos info"
   collect _ = []
 
-ensureNoDuplicates :: [(Qualified Ident, SourcePos)] -> Either ErrorStack ()
+ensureNoDuplicates :: [(Qualified Ident, SourceSpan)] -> Either ErrorStack ()
 ensureNoDuplicates m = go $ sortBy (compare `on` fst) m
   where
   go [] = return ()
diff --git a/src/Language/PureScript/TypeChecker.hs b/src/Language/PureScript/TypeChecker.hs
--- a/src/Language/PureScript/TypeChecker.hs
+++ b/src/Language/PureScript/TypeChecker.hs
@@ -53,6 +53,7 @@
 addDataConstructor :: ModuleName -> DataDeclType -> ProperName -> [String] -> ProperName -> [Type] -> Check ()
 addDataConstructor moduleName dtype name args dctor tys = do
   env <- getEnv
+  mapM_ checkTypeSynonyms tys
   let retTy = foldl TypeApp (TypeConstructor (Qualified (Just moduleName) name)) (map TypeVar args)
   let dctorTy = foldr function retTy tys
   let polyType = mkForAll args dctorTy
@@ -61,6 +62,7 @@
 addTypeSynonym :: ModuleName -> ProperName -> [(String, Maybe Kind)] -> Type -> Kind -> Check ()
 addTypeSynonym moduleName name args ty kind = do
   env <- getEnv
+  checkTypeSynonyms ty
   putEnv $ env { types = M.insert (Qualified (Just moduleName) name) (kind, TypeSynonym) (types env)
                , typeSynonyms = M.insert (Qualified (Just moduleName) name) (args, ty) (typeSynonyms env) }
 
@@ -105,6 +107,12 @@
   return ()
 checkTypeClassInstance m (TypeApp t1 t2) = checkTypeClassInstance m t1 >> checkTypeClassInstance m t2
 checkTypeClassInstance _ ty = throwError $ mkErrorStack "Type class instance head is invalid." (Just (TypeError ty))
+
+-- |
+-- Check that type synonyms are fully-applied in a type
+--
+checkTypeSynonyms :: Type -> Check ()
+checkTypeSynonyms = void . replaceAllTypeSynonyms
 
 -- |
 -- Type check all declarations in a module