From eb90a4091c1f2586640ee49d6f91fc83c05239f6 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Sun, 24 May 2020 13:51:00 +0200
Subject: [PATCH] Check point

---
 CHANGELOG.md                                 | 17 ++--
 src/Language/GraphQL/AST/Core.hs             | 21 +----
 src/Language/GraphQL/Execute/Coerce.hs       | 63 +++++++-------
 src/Language/GraphQL/Execute/Transform.hs    | 45 +++++-----
 src/Language/GraphQL/Schema.hs               | 87 +++++++++-----------
 src/Language/GraphQL/Trans.hs                |  7 +-
 src/Language/GraphQL/Type.hs                 | 63 --------------
 src/Language/GraphQL/Type/Definition.hs      | 20 ++---
 src/Language/GraphQL/Type/Directive.hs       |  5 +-
 src/Language/GraphQL/Type/In.hs              | 26 ++++++
 src/Language/GraphQL/Type/Out.hs             | 58 +++++++++++++
 tests/Language/GraphQL/Execute/CoerceSpec.hs | 35 ++++----
 tests/Language/GraphQL/SchemaSpec.hs         |  7 +-
 tests/Language/GraphQL/Type/OutSpec.hs       | 15 ++++
 tests/Test/DirectiveSpec.hs                  |  3 +-
 tests/Test/FragmentSpec.hs                   | 16 ++--
 tests/Test/RootOperationSpec.hs              | 11 ++-
 tests/Test/StarWars/Schema.hs                | 53 ++++++------
 18 files changed, 281 insertions(+), 271 deletions(-)
 delete mode 100644 src/Language/GraphQL/Type.hs
 create mode 100644 src/Language/GraphQL/Type/In.hs
 create mode 100644 src/Language/GraphQL/Type/Out.hs
 create mode 100644 tests/Language/GraphQL/Type/OutSpec.hs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66a3c5d..11e63bc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,27 +10,32 @@ and this project adheres to
 ### Fixed
 - The parser rejects variables when parsing defaultValue (DefaultValue). The
   specification defines default values as `Value` with `const` parameter and
-  constant cannot be variables. `AST.Document.ConstValue` was added,
+  constants cannot be variables. `AST.Document.ConstValue` was added,
   `AST.Document.ObjectField` was modified.
 - AST transformation should never fail.
     * Missing variable are assumed to be null.
     * Invalid (recusrive or non-existing) fragments should be skipped.
 
 ### Changed
-- `Resolver` is now `Resolver Name FieldResolver` where `FieldResolver` can
-  contain a JSON value or another resolver, which is invoked during the
-  execution. `FieldResolver` is executed in `ActionT` and the current `Field` is
-  passed in the reader and not as an explicit argument.
+- `Schema.Resolver` cannot return arbitrary JSON anymore, but only
+  `Type.Out.Value`.
+- `Schema.object` takes an array of field resolvers (name, value pairs) and
+  returns a resolver (just the function). There is no need in special functions
+  to construct field resolvers anymore, they can be constructed with just
+  `Resolver "fieldName" $ pure $ object [...]`.
 - `Execute.Transform.operation` has the prior responsibility of
   `Execute.Transform.document`, but transforms only the chosen operation and not
   the whole document. `Execute.Transform.document` translates
   `AST.Document.Document` into `Execute.Transform.Document`.
+- `AST.Core.Value` was moved into `Type.In`. Input values are used only in the
+  execution and type system, it is not a part of the parsing tree.
 
 ### Added
 - `Type.Definition` contains input and the most output types.
 - `Type.Schema` describes a schema. Both public functions that execute queries
   accept a `Schema` now instead of a `HashMap`. The execution fails if the root
   operation doesn't match the root Query type in the schema.
+- `Type.In` and `Type.Out`.
 - `Execute.Coerce` defines a typeclass responsible for input, variable value
   coercion. It decouples us a bit from JSON since any format can be used to pass
   query variables. Execution functions accept (`HashMap Name a`) instead of
@@ -45,6 +50,8 @@ and this project adheres to
   converted to JSON and JSON is not suitable as an internal representation for
   GraphQL. E.g. GraphQL distinguishes between Floats and Integersa and we need
   a way to represent objects as a "Field Name -> Resolver" map.
+- `Schema.wrappedObject`. `Schema.object` creates now wrapped objects.
+- `Type` module. Superseded by `Type.Out`.
 
 ## [0.7.0.0] - 2020-05-11
 ### Fixed
diff --git a/src/Language/GraphQL/AST/Core.hs b/src/Language/GraphQL/AST/Core.hs
index d719912..6dcfb81 100644
--- a/src/Language/GraphQL/AST/Core.hs
+++ b/src/Language/GraphQL/AST/Core.hs
@@ -9,15 +9,13 @@ module Language.GraphQL.AST.Core
     , Operation(..)
     , Selection(..)
     , TypeCondition
-    , Value(..)
     ) where
 
-import Data.Int (Int32)
 import Data.HashMap.Strict (HashMap)
 import Data.Sequence (Seq)
-import Data.String (IsString(..))
 import Data.Text (Text)
 import Language.GraphQL.AST (Alias, Name, TypeCondition)
+import qualified Language.GraphQL.Type.In as In
 
 -- | GraphQL has 3 operation types: queries, mutations and subscribtions.
 --
@@ -33,7 +31,7 @@ data Field
     deriving (Eq, Show)
 
 -- | Argument list.
-newtype Arguments = Arguments (HashMap Name Value)
+newtype Arguments = Arguments (HashMap Name In.Value)
     deriving (Eq, Show)
 
 instance Semigroup Arguments where
@@ -56,18 +54,3 @@ data Selection
     = SelectionFragment Fragment
     | SelectionField Field
     deriving (Eq, Show)
-
--- | Represents accordingly typed GraphQL values.
-data Value
-    = Int Int32
-    | Float Double -- ^ GraphQL Float is double precision
-    | String Text
-    | Boolean Bool
-    | Null
-    | Enum Name
-    | List [Value]
-    | Object (HashMap Name Value)
-    deriving (Eq, Show)
-
-instance IsString Value where
-    fromString = String . fromString
diff --git a/src/Language/GraphQL/Execute/Coerce.hs b/src/Language/GraphQL/Execute/Coerce.hs
index 6997945..32c48fd 100644
--- a/src/Language/GraphQL/Execute/Coerce.hs
+++ b/src/Language/GraphQL/Execute/Coerce.hs
@@ -15,7 +15,8 @@ import qualified Data.Text.Lazy as Text.Lazy
 import qualified Data.Text.Lazy.Builder as Text.Builder
 import qualified Data.Text.Lazy.Builder.Int as Text.Builder
 import Data.Scientific (toBoundedInteger, toRealFloat)
-import Language.GraphQL.AST.Core
+import Language.GraphQL.AST.Document (Name)
+import qualified Language.GraphQL.Type.In as In
 import Language.GraphQL.Schema
 import Language.GraphQL.Type.Definition
 
@@ -46,26 +47,26 @@ class VariableValue a where
     coerceVariableValue
         :: InputType -- ^ Expected type (variable type given in the query).
         -> a -- ^ Variable value being coerced.
-        -> Maybe Value -- ^ Coerced value on success, 'Nothing' otherwise.
+        -> Maybe In.Value -- ^ Coerced value on success, 'Nothing' otherwise.
 
 instance VariableValue Aeson.Value where
-    coerceVariableValue _ Aeson.Null = Just Null
+    coerceVariableValue _ Aeson.Null = Just In.Null
     coerceVariableValue (ScalarInputTypeDefinition scalarType) value
-        | (Aeson.String stringValue) <- value = Just $ String stringValue
-        | (Aeson.Bool booleanValue) <- value = Just $ Boolean booleanValue
+        | (Aeson.String stringValue) <- value = Just $ In.String stringValue
+        | (Aeson.Bool booleanValue) <- value = Just $ In.Boolean booleanValue
         | (Aeson.Number numberValue) <- value
         , (ScalarType "Float" _) <- scalarType =
-            Just $ Float $ toRealFloat numberValue
+            Just $ In.Float $ toRealFloat numberValue
         | (Aeson.Number numberValue) <- value = -- ID or Int
-            Int <$> toBoundedInteger numberValue
+            In.Int <$> toBoundedInteger numberValue
     coerceVariableValue (EnumInputTypeDefinition _) (Aeson.String stringValue) =
-        Just $ Enum stringValue
+        Just $ In.Enum stringValue
     coerceVariableValue (ObjectInputTypeDefinition objectType) value
         | (Aeson.Object objectValue) <- value = do
             let (InputObjectType _ _ inputFields) = objectType
             (newObjectValue, resultMap) <- foldWithKey objectValue inputFields
             if HashMap.null newObjectValue
-                then Just $ Object resultMap
+                then Just $ In.Object resultMap
                 else Nothing
       where
         foldWithKey objectValue = HashMap.foldrWithKey matchFieldValues
@@ -81,7 +82,7 @@ instance VariableValue Aeson.Value where
                         pure (newObjectValue, insert coerced)
                     Nothing -> Just (objectValue, resultMap)
     coerceVariableValue (ListInputTypeDefinition listType) value
-        | (Aeson.Array arrayValue) <- value = List
+        | (Aeson.Array arrayValue) <- value = In.List
             <$> foldr foldVector (Just []) arrayValue
         | otherwise = coerceVariableValue listType value
       where
@@ -95,7 +96,7 @@ instance VariableValue Aeson.Value where
 --   corresponding types.
 coerceInputLiterals
     :: HashMap Name InputType
-    -> HashMap Name Value
+    -> HashMap Name In.Value
     -> Maybe Subs
 coerceInputLiterals variableTypes variableValues =
     foldWithKey operator variableTypes
@@ -105,34 +106,34 @@ coerceInputLiterals variableTypes variableValues =
         <$> (lookupVariable variableName >>= coerceInputLiteral variableType)
         <*> resultMap
     coerceInputLiteral (ScalarInputType type') value
-        | (String stringValue) <- value
-        , (ScalarType "String" _) <- type' = Just $ String stringValue
-        | (Boolean booleanValue) <- value
-        , (ScalarType "Boolean" _) <- type' = Just $ Boolean booleanValue
-        | (Int intValue) <- value
-        , (ScalarType "Int" _) <- type' = Just $ Int intValue
-        | (Float floatValue) <- value
-        , (ScalarType "Float" _) <- type' = Just $ Float floatValue
-        | (Int intValue) <- value
+        | (In.String stringValue) <- value
+        , (ScalarType "String" _) <- type' = Just $ In.String stringValue
+        | (In.Boolean booleanValue) <- value
+        , (ScalarType "Boolean" _) <- type' = Just $ In.Boolean booleanValue
+        | (In.Int intValue) <- value
+        , (ScalarType "Int" _) <- type' = Just $ In.Int intValue
+        | (In.Float floatValue) <- value
+        , (ScalarType "Float" _) <- type' = Just $ In.Float floatValue
+        | (In.Int intValue) <- value
         , (ScalarType "Float" _) <- type' =
-            Just $ Float $ fromIntegral intValue
-        | (String stringValue) <- value
-        , (ScalarType "ID" _) <- type' = Just $ String stringValue
-        | (Int intValue) <- value
+            Just $ In.Float $ fromIntegral intValue
+        | (In.String stringValue) <- value
+        , (ScalarType "ID" _) <- type' = Just $ In.String stringValue
+        | (In.Int intValue) <- value
         , (ScalarType "ID" _) <- type' = Just $ decimal intValue
-    coerceInputLiteral (EnumInputType type') (Enum enumValue)
-        | member enumValue type' = Just $ Enum enumValue
-    coerceInputLiteral (ObjectInputType type') (Object _) = 
+    coerceInputLiteral (EnumInputType type') (In.Enum enumValue)
+        | member enumValue type' = Just $ In.Enum enumValue
+    coerceInputLiteral (ObjectInputType type') (In.Object _) = 
         let (InputObjectType _ _ inputFields) = type'
-            in Object <$> foldWithKey matchFieldValues inputFields
+            in In.Object <$> foldWithKey matchFieldValues inputFields
     coerceInputLiteral _ _ = Nothing
     member value (EnumType _ _ members) = Set.member value members
     matchFieldValues fieldName (InputField _ type' defaultValue) resultMap =
         case lookupVariable fieldName of
-            Just Null
+            Just In.Null
                 | isNonNullInputType type' -> Nothing
                 | otherwise ->
-                    HashMap.insert fieldName Null <$> resultMap
+                    HashMap.insert fieldName In.Null <$> resultMap
             Just variableValue -> HashMap.insert fieldName
                 <$> coerceInputLiteral type' variableValue
                 <*> resultMap
@@ -144,7 +145,7 @@ coerceInputLiterals variableTypes variableValues =
                 | otherwise -> resultMap
     lookupVariable = flip HashMap.lookup variableValues
     foldWithKey f = HashMap.foldrWithKey f (Just HashMap.empty)
-    decimal = String
+    decimal = In.String
         . Text.Lazy.toStrict
         . Text.Builder.toLazyText
         . Text.Builder.decimal
diff --git a/src/Language/GraphQL/Execute/Transform.hs b/src/Language/GraphQL/Execute/Transform.hs
index df64254..9768675 100644
--- a/src/Language/GraphQL/Execute/Transform.hs
+++ b/src/Language/GraphQL/Execute/Transform.hs
@@ -32,6 +32,7 @@ import Language.GraphQL.Execute.Coerce
 import qualified Language.GraphQL.Schema as Schema
 import qualified Language.GraphQL.Type.Definition as Definition
 import qualified Language.GraphQL.Type.Directive as Directive
+import qualified Language.GraphQL.Type.In as In
 import Language.GraphQL.Type.Schema
 
 -- | Associates a fragment name with a list of 'Core.Field's.
@@ -136,23 +137,23 @@ coerceVariableValues schema operationDefinition variableValues' =
             <*> coercedValues
     choose Nothing defaultValue variableType
         | Just _ <- defaultValue = defaultValue
-        | not (isNonNullInputType variableType) = Just Core.Null
+        | not (isNonNullInputType variableType) = Just In.Null
     choose (Just value') _ variableType
         | Just coercedValue <- coerceVariableValue variableType value'
-        , not (isNonNullInputType variableType) || coercedValue /= Core.Null =
+        , not (isNonNullInputType variableType) || coercedValue /= In.Null =
             Just coercedValue
     choose _ _ _ = Nothing
 
-constValue :: Full.ConstValue -> Core.Value
-constValue (Full.ConstInt i) = Core.Int i
-constValue (Full.ConstFloat f) = Core.Float f
-constValue (Full.ConstString x) = Core.String x
-constValue (Full.ConstBoolean b) = Core.Boolean b
-constValue Full.ConstNull = Core.Null
-constValue (Full.ConstEnum e) = Core.Enum e
-constValue (Full.ConstList l) = Core.List $ constValue <$> l
+constValue :: Full.ConstValue -> In.Value
+constValue (Full.ConstInt i) = In.Int i
+constValue (Full.ConstFloat f) = In.Float f
+constValue (Full.ConstString x) = In.String x
+constValue (Full.ConstBoolean b) = In.Boolean b
+constValue Full.ConstNull = In.Null
+constValue (Full.ConstEnum e) = In.Enum e
+constValue (Full.ConstList l) = In.List $ constValue <$> l
 constValue (Full.ConstObject o) =
-    Core.Object $ HashMap.fromList $ constObjectField <$> o
+    In.Object $ HashMap.fromList $ constObjectField <$> o
   where
     constObjectField (Full.ObjectField key value') = (key, constValue value')
 
@@ -294,19 +295,19 @@ arguments = fmap Core.Arguments . foldM go HashMap.empty
         substitutedValue <- value value'
         return $ HashMap.insert name substitutedValue arguments'
 
-value :: Full.Value -> TransformT Core.Value
+value :: Full.Value -> TransformT In.Value
 value (Full.Variable name) =
-    gets $ fromMaybe Core.Null . HashMap.lookup name . variableValues
-value (Full.Int i) = pure $ Core.Int i
-value (Full.Float f) = pure $ Core.Float f
-value (Full.String x) = pure $ Core.String x
-value (Full.Boolean b) = pure $ Core.Boolean b
-value Full.Null = pure   Core.Null
-value (Full.Enum e) = pure $ Core.Enum e
+    gets $ fromMaybe In.Null . HashMap.lookup name . variableValues
+value (Full.Int i) = pure $ In.Int i
+value (Full.Float f) = pure $ In.Float f
+value (Full.String x) = pure $ In.String x
+value (Full.Boolean b) = pure $ In.Boolean b
+value Full.Null = pure   In.Null
+value (Full.Enum e) = pure $ In.Enum e
 value (Full.List l) =
-    Core.List <$> traverse value l
+    In.List <$> traverse value l
 value (Full.Object o) =
-    Core.Object . HashMap.fromList <$> traverse objectField o
+    In.Object . HashMap.fromList <$> traverse objectField o
 
-objectField :: Full.ObjectField Full.Value -> TransformT (Core.Name, Core.Value)
+objectField :: Full.ObjectField Full.Value -> TransformT (Core.Name, In.Value)
 objectField (Full.ObjectField name value') = (name,) <$> value value'
diff --git a/src/Language/GraphQL/Schema.hs b/src/Language/GraphQL/Schema.hs
index 69f697e..34abf10 100644
--- a/src/Language/GraphQL/Schema.hs
+++ b/src/Language/GraphQL/Schema.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE ExplicitForAll #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 -- | This module provides a representation of a @GraphQL@ Schema in addition to
@@ -8,10 +9,6 @@ module Language.GraphQL.Schema
     , object
     , resolve
     , resolversToMap
-    , wrappedObject
-    -- * AST Reexports
-    , Field
-    , Value(..)
     ) where
 
 import Control.Monad.Trans.Class (lift)
@@ -28,38 +25,35 @@ import qualified Data.Text as T
 import Language.GraphQL.AST.Core
 import Language.GraphQL.Error
 import Language.GraphQL.Trans
-import qualified Language.GraphQL.Type.Definition as Definition
-import qualified Language.GraphQL.Type as Type
+import qualified Language.GraphQL.Type.In as In
+import qualified Language.GraphQL.Type.Out as Out
 
 -- | Resolves a 'Field' into an @Aeson.@'Data.Aeson.Types.Object' with error
---   information (if an error has occurred). @m@ is an arbitrary monad, usually
---   'IO'.
-data Resolver m = Resolver Name (Definition.FieldResolver m)
+-- information (if an error has occurred). @m@ is an arbitrary monad, usually
+-- 'IO'.
+--
+-- Resolving a field can result in a leaf value or an object, which is
+-- represented as a list of nested resolvers, used to resolve the fields of that
+-- object.
+data Resolver m = Resolver Name (ActionT m (Out.Value m))
 
 -- | Converts resolvers to a map.
 resolversToMap :: (Foldable f, Functor f)
-    => f (Resolver m)
-    -> HashMap Text (Definition.FieldResolver m)
+    => forall m
+    . f (Resolver m)
+    -> HashMap Text (ActionT m (Out.Value m))
 resolversToMap = HashMap.fromList . toList . fmap toKV
   where
     toKV (Resolver name r) = (name, r)
 
 -- | Contains variables for the query. The key of the map is a variable name,
 --   and the value is the variable value.
-type Subs = HashMap Name Value
+type Subs = HashMap Name In.Value
 
--- | Like 'object' but can be null or a list of objects.
-wrappedObject :: Monad m
-    => Name
-    -> ActionT m (Type.Wrapping (Definition.FieldResolver m))
-    -> Resolver m
-wrappedObject name = Resolver name . Definition.NestingResolver
-
--- | Create a new 'Resolver' with the given 'Name' from the given 'Resolver's.
-object :: Monad m
-    => [Resolver m]
-    -> Type.Wrapping (Definition.FieldResolver m)
-object = Type.O . resolversToMap
+-- | Create a new 'Resolver' with the given 'Name' from the given
+-- Resolver's.
+object :: Monad m => [Resolver m] -> Out.Value m
+object = Out.Object . resolversToMap
 
 resolveFieldValue :: Monad m => Field -> ActionT m a -> m (Either Text a)
 resolveFieldValue field@(Field _ _ args _) =
@@ -69,26 +63,25 @@ resolveFieldValue field@(Field _ _ args _) =
 
 withField :: Monad m
     => Field
-    -> Definition.FieldResolver m
+    -> ActionT m (Out.Value m)
     -> CollectErrsT m Aeson.Object
-withField field (Definition.ValueResolver resolver) = do
-    answer <- lift $ resolveFieldValue field resolver
-    either (errmsg field) (pure . HashMap.singleton (aliasOrName field)) answer
-withField field (Definition.NestingResolver resolver) = do
+withField field resolver = do
     answer <- lift $ resolveFieldValue field resolver
     case answer of
-        Right result -> HashMap.singleton (aliasOrName field) <$> toJSON field result
+        Right result -> HashMap.singleton (aliasOrName field)
+            <$> toJSON field result
         Left errorMessage -> errmsg field errorMessage
 
-toJSON :: Monad m => Field -> Type.Wrapping (Definition.FieldResolver m) -> CollectErrsT m Aeson.Value
-toJSON _ Type.Null = pure Aeson.Null
-toJSON _ (Type.I i) = pure $ Aeson.toJSON i
-toJSON _ (Type.B i) = pure $ Aeson.toJSON i
-toJSON _ (Type.F i) = pure $ Aeson.toJSON i
-toJSON _ (Type.E i) = pure $ Aeson.toJSON i
-toJSON _ (Type.S i) = pure $ Aeson.toJSON i
-toJSON field (Type.List list) = Aeson.toJSON <$> traverse (toJSON field) list
-toJSON (Field _ _ _ seqSelection) (Type.O map') = map' `resolve` seqSelection
+toJSON :: Monad m => Field -> Out.Value m -> CollectErrsT m Aeson.Value
+toJSON _ Out.Null = pure Aeson.Null
+toJSON _ (Out.Int integer) = pure $ Aeson.toJSON integer
+toJSON _ (Out.Boolean boolean) = pure $ Aeson.Bool boolean
+toJSON _ (Out.Float float) = pure $ Aeson.toJSON float
+toJSON _ (Out.Enum enum) = pure $ Aeson.String enum
+toJSON _ (Out.String string) = pure $ Aeson.String string
+toJSON field (Out.List list) = Aeson.toJSON <$> traverse (toJSON field) list
+toJSON (Field _ _ _ seqSelection) (Out.Object map') =
+    map' `resolve` seqSelection
 
 errmsg :: Monad m => Field -> Text -> CollectErrsT m (HashMap Text Aeson.Value)
 errmsg field errorMessage = do
@@ -96,10 +89,10 @@ errmsg field errorMessage = do
     pure $ HashMap.singleton (aliasOrName field) Aeson.Null
 
 -- | Takes a list of 'Resolver's and a list of 'Field's and applies each
---   'Resolver' to each 'Field'. Resolves into a value containing the
---   resolved 'Field', or a null value and error information.
+-- 'Resolver' to each 'Field'. Resolves into a value containing the
+-- resolved 'Field', or a null value and error information.
 resolve :: Monad m
-    => HashMap Text (Definition.FieldResolver m)
+    => HashMap Text (ActionT m (Out.Value m))
     -> Seq Selection
     -> CollectErrsT m Aeson.Value
 resolve resolvers = fmap (Aeson.toJSON . fold) . traverse tryResolvers
@@ -109,17 +102,11 @@ resolve resolvers = fmap (Aeson.toJSON . fold) . traverse tryResolvers
         | (Just resolver) <- lookupResolver name = withField fld resolver
         | otherwise = errmsg fld $ T.unwords ["field", name, "not resolved."]
     tryResolvers (SelectionFragment (Fragment typeCondition selections'))
-        | Just (Definition.ValueResolver resolver) <- lookupResolver "__typename" = do
-            let fakeField = Field Nothing "__typename" mempty mempty
-            that <- lift $ resolveFieldValue fakeField resolver
-            if Right (Aeson.String typeCondition) == that
-                then fmap fold . traverse tryResolvers $ selections'
-                else pure mempty
-        | Just (Definition.NestingResolver resolver) <- lookupResolver "__typename" = do
+        | Just resolver <- lookupResolver "__typename" = do
             let fakeField = Field Nothing "__typename" mempty mempty
             that <- lift $ resolveFieldValue fakeField resolver
             case that of
-                Right (Type.S typeCondition')
+                Right (Out.String typeCondition')
                     | typeCondition' == typeCondition ->
                         fmap fold . traverse tryResolvers $ selections'
                 _ -> pure mempty
diff --git a/src/Language/GraphQL/Trans.hs b/src/Language/GraphQL/Trans.hs
index f09a8a0..3c3ffa4 100644
--- a/src/Language/GraphQL/Trans.hs
+++ b/src/Language/GraphQL/Trans.hs
@@ -15,6 +15,7 @@ import qualified Data.HashMap.Strict as HashMap
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
 import Language.GraphQL.AST.Core
+import qualified Language.GraphQL.Type.In as In
 import Prelude hiding (lookup)
 
 -- | Resolution context holds resolver arguments.
@@ -55,11 +56,11 @@ instance Monad m => MonadPlus (ActionT m) where
     mplus = (<|>)
 
 -- | Retrieves an argument by its name. If the argument with this name couldn't
---   be found, returns 'Value.Null' (i.e. the argument is assumed to
+--   be found, returns 'In.Null' (i.e. the argument is assumed to
 --   be optional then).
-argument :: Monad m => Name -> ActionT m Value
+argument :: Monad m => Name -> ActionT m In.Value
 argument argumentName = do
     argumentValue <- ActionT $ lift $ asks $ lookup . arguments
-    pure $ fromMaybe Null argumentValue
+    pure $ fromMaybe In.Null argumentValue
   where
     lookup (Arguments argumentMap) = HashMap.lookup argumentName argumentMap
diff --git a/src/Language/GraphQL/Type.hs b/src/Language/GraphQL/Type.hs
deleted file mode 100644
index 12b38dc..0000000
--- a/src/Language/GraphQL/Type.hs
+++ /dev/null
@@ -1,63 +0,0 @@
--- | Definitions for @GraphQL@ input types.
-module Language.GraphQL.Type
-    ( Wrapping(..)
-    ) where
-
-import Data.HashMap.Strict (HashMap)
-import Data.Text (Text)
-import Language.GraphQL.AST.Document (Name)
-
--- | GraphQL distinguishes between "wrapping" and "named" types. Each wrapping
---   type can wrap other wrapping or named types. Wrapping types are lists and
---   Non-Null types (named types are nullable by default).
---
---   This 'Wrapping' type doesn\'t reflect this distinction exactly but it is
---   used in the resolvers to take into account that the returned value can be
---   nullable or an (arbitrary nested) list.
-data Wrapping a
-    = List [Wrapping a] -- ^ Arbitrary nested list
---    | Named a -- ^ Named type without further wrapping
-    | Null -- ^ Null
-    | O (HashMap Name a)
-    | I Int
-    | B Bool
-    | F Float
-    | E Text
-    | S Text
-    deriving (Eq, Show)
-
-instance Functor Wrapping where
-    fmap f (List list) = List $ fmap (fmap f) list
-    fmap f (O map') = O $ f <$> map'
-    fmap _ Null = Null
-    fmap _ (I i) = I i
-    fmap _ (B i) = B i
-    fmap _ (F i) = F i
-    fmap _ (E i) = E i
-    fmap _ (S i) = S i
-
-    {-instance Foldable Wrapping where
-    foldr f acc (List list) = foldr (flip $ foldr f) acc list
-    foldr f acc (O map') = foldr f acc map'
-    foldr _ acc _ = acc -}
-
-    {-instance Traversable Wrapping where
-    traverse f (List list) = List <$> traverse (traverse f) list
-    traverse f (Named named) = Named <$> f named
-    traverse _ Null = pure Null
-    traverse f (O map') = O <$> traverse f map'-}
-
-{-instance Applicative Wrapping where
-    pure = Named
-    Null <*> _ = Null
-    _ <*> Null = Null
-    (Named f) <*> (Named x) = Named $ f x
-    (List fs) <*> (List xs) = List $ (<*>) <$> fs <*> xs
-    (Named f) <*> list = f <$> list
-    (List fs) <*> named = List $ (<*> named) <$> fs
-
-instance Monad Wrapping where
-    return = pure
-    Null >>= _ = Null
-    (Named x) >>= f = f x
-    (List xs) >>= f = List $ fmap (>>= f) xs-}
diff --git a/src/Language/GraphQL/Type/Definition.hs b/src/Language/GraphQL/Type/Definition.hs
index 559611b..54eac85 100644
--- a/src/Language/GraphQL/Type/Definition.hs
+++ b/src/Language/GraphQL/Type/Definition.hs
@@ -8,7 +8,6 @@ module Language.GraphQL.Type.Definition
     ( Argument(..)
     , EnumType(..)
     , Field(..)
-    , FieldResolver(..)
     , InputField(..)
     , InputObjectType(..)
     , InputType(..)
@@ -31,13 +30,13 @@ module Language.GraphQL.Type.Definition
     , string
     ) where
 
-import qualified Data.Aeson as Aeson
 import Data.HashMap.Strict (HashMap)
 import Data.Set (Set)
 import Data.Text (Text)
-import Language.GraphQL.AST.Core (Name, Value)
+import Language.GraphQL.AST.Document (Name)
 import Language.GraphQL.Trans
-import qualified Language.GraphQL.Type as Type
+import qualified Language.GraphQL.Type.In as In
+import qualified Language.GraphQL.Type.Out as Out
 import Prelude hiding (id)
 
 -- | Object type definition.
@@ -51,17 +50,10 @@ data Field m = Field
     (Maybe Text) -- ^ Description.
     (OutputType m) -- ^ Field type.
     (HashMap Name Argument) -- ^ Arguments.
-    (FieldResolver m) -- ^ Resolver.
-
--- | Resolving a field can result in a leaf value or an object, which is
--- represented as a list of nested resolvers, used to resolve the fields of that
--- object.
-data FieldResolver m
-    = ValueResolver (ActionT m Aeson.Value)
-    | NestingResolver (ActionT m (Type.Wrapping (FieldResolver m)))
+    (ActionT m (Out.Value m)) -- ^ Resolver.
 
 -- | Field argument definition.
-data Argument = Argument (Maybe Text) InputType (Maybe Value)
+data Argument = Argument (Maybe Text) InputType (Maybe In.Value)
 
 -- | Scalar type definition.
 --
@@ -77,7 +69,7 @@ data ScalarType = ScalarType Name (Maybe Text)
 data EnumType = EnumType Name (Maybe Text) (Set Text)
 
 -- | Single field of an 'InputObjectType'.
-data InputField = InputField (Maybe Text) InputType (Maybe Value)
+data InputField = InputField (Maybe Text) InputType (Maybe In.Value)
 
 -- | Input object type definition.
 --
diff --git a/src/Language/GraphQL/Type/Directive.hs b/src/Language/GraphQL/Type/Directive.hs
index afd97da..9675df8 100644
--- a/src/Language/GraphQL/Type/Directive.hs
+++ b/src/Language/GraphQL/Type/Directive.hs
@@ -6,6 +6,7 @@ module Language.GraphQL.Type.Directive
 
 import qualified Data.HashMap.Strict as HashMap
 import Language.GraphQL.AST.Core
+import qualified Language.GraphQL.Type.In as In
 
 -- | Directive processing status.
 data Status
@@ -36,7 +37,7 @@ skip = handle skip'
   where
     skip' directive'@(Directive "skip" (Arguments arguments)) =
         case HashMap.lookup "if" arguments of
-            (Just (Boolean True)) -> Skip
+            (Just (In.Boolean True)) -> Skip
             _ -> Include directive'
     skip' directive' = Continue directive'
 
@@ -45,6 +46,6 @@ include = handle include'
   where
     include' directive'@(Directive "include" (Arguments arguments)) =
         case HashMap.lookup "if" arguments of
-            (Just (Boolean True)) -> Include directive'
+            (Just (In.Boolean True)) -> Include directive'
             _ -> Skip
     include' directive' = Continue directive'
diff --git a/src/Language/GraphQL/Type/In.hs b/src/Language/GraphQL/Type/In.hs
new file mode 100644
index 0000000..a6d35e2
--- /dev/null
+++ b/src/Language/GraphQL/Type/In.hs
@@ -0,0 +1,26 @@
+-- | This module is intended to be imported qualified, to avoid name clashes
+-- with 'Language.GraphQL.Type.Out'.
+module Language.GraphQL.Type.In
+    ( Value(..)
+    ) where
+
+import Data.HashMap.Strict (HashMap)
+import Data.Int (Int32)
+import Data.String (IsString(..))
+import Data.Text (Text)
+import Language.GraphQL.AST.Document (Name)
+
+-- | Represents accordingly typed GraphQL values.
+data Value
+    = Int Int32
+    | Float Double -- ^ GraphQL Float is double precision
+    | String Text
+    | Boolean Bool
+    | Null
+    | Enum Name
+    | List [Value]
+    | Object (HashMap Name Value)
+    deriving (Eq, Show)
+
+instance IsString Value where
+    fromString = String . fromString
diff --git a/src/Language/GraphQL/Type/Out.hs b/src/Language/GraphQL/Type/Out.hs
new file mode 100644
index 0000000..96bc9cf
--- /dev/null
+++ b/src/Language/GraphQL/Type/Out.hs
@@ -0,0 +1,58 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+-- | This module is intended to be imported qualified, to avoid name clashes
+-- with 'Language.GraphQL.Type.In'.
+module Language.GraphQL.Type.Out
+    ( Value(..)
+    ) where
+
+import Data.HashMap.Strict (HashMap)
+import qualified Data.HashMap.Strict as HashMap
+import Data.Int (Int32)
+import Data.String (IsString(..))
+import Data.Text (Text)
+import qualified Data.Text as Text
+import Language.GraphQL.AST.Document (Name)
+import Language.GraphQL.Trans
+
+-- | GraphQL distinguishes between "wrapping" and "named" types. Each wrapping
+-- type can wrap other wrapping or named types. Wrapping types are lists and
+-- Non-Null types (named types are nullable by default).
+--
+-- This 'Value' type doesn\'t reflect this distinction exactly but it is used
+-- in the resolvers to take into account that the returned value can be nullable
+-- or an (arbitrary nested) list.
+data Value m
+    = Int Int32
+    | Float Double
+    | String Text
+    | Boolean Bool
+    | Null
+    | Enum Name
+    | List [Value m] -- ^ Arbitrary nested list.
+    | Object (HashMap Name (ActionT m (Value m)))
+
+instance IsString (Value m) where
+    fromString = String . fromString
+
+instance Show (Value m) where
+    show (Int integer) = "Int " ++ show integer
+    show (Float float) = "Float " ++ show float
+    show (String text) = Text.unpack $ "String " <> text
+    show (Boolean True) = "Boolean True"
+    show (Boolean False) = "Boolean False"
+    show Null = "Null"
+    show (Enum enum) = Text.unpack $ "Enum " <> enum
+    show (List list) = show list
+    show (Object object) = Text.unpack
+        $ "Object [" <> Text.intercalate ", " (HashMap.keys object) <> "]"
+
+instance Eq (Value m) where
+    (Int this) == (Int that) = this == that
+    (Float this) == (Float that) = this == that
+    (String this) == (String that) = this == that
+    (Boolean this) == (Boolean that) = this == that
+    (Enum this) == (Enum that) = this == that
+    (List this) == (List that) = this == that
+    (Object this) == (Object that) = HashMap.keys this == HashMap.keys that
+    _ == _ = False
diff --git a/tests/Language/GraphQL/Execute/CoerceSpec.hs b/tests/Language/GraphQL/Execute/CoerceSpec.hs
index 2ddab0c..57f740b 100644
--- a/tests/Language/GraphQL/Execute/CoerceSpec.hs
+++ b/tests/Language/GraphQL/Execute/CoerceSpec.hs
@@ -15,6 +15,7 @@ import Language.GraphQL.AST.Core
 import Language.GraphQL.Execute.Coerce
 import Language.GraphQL.Schema
 import Language.GraphQL.Type.Definition
+import qualified Language.GraphQL.Type.In as In
 import Prelude hiding (id)
 import Test.Hspec (Spec, describe, it, shouldBe, shouldSatisfy)
 
@@ -22,12 +23,12 @@ direction :: EnumType
 direction = EnumType "Direction" Nothing 
     $ Set.fromList ["NORTH", "EAST", "SOUTH", "WEST"]
 
-coerceInputLiteral :: InputType -> Value -> Maybe Subs
+coerceInputLiteral :: InputType -> In.Value -> Maybe Subs
 coerceInputLiteral input value = coerceInputLiterals
     (HashMap.singleton "variableName" input)
     (HashMap.singleton "variableName" value)
 
-lookupActual :: Maybe (HashMap Name Value) -> Maybe Value
+lookupActual :: Maybe (HashMap Name In.Value) -> Maybe In.Value
 lookupActual = (HashMap.lookup "variableName" =<<)
 
 singletonInputObject :: InputType
@@ -41,22 +42,22 @@ spec :: Spec
 spec = do
     describe "ToGraphQL Aeson" $ do
         it "coerces strings" $
-            let expected = Just (String "asdf")
+            let expected = Just (In.String "asdf")
                 actual = coerceVariableValue
                     (ScalarInputType string) (Aeson.String "asdf")
              in actual `shouldBe` expected
         it "coerces non-null strings" $
-            let expected = Just (String "asdf")
+            let expected = Just (In.String "asdf")
                 actual = coerceVariableValue
                     (NonNullScalarInputType string) (Aeson.String "asdf")
              in actual `shouldBe` expected
         it "coerces booleans" $
-            let expected = Just (Boolean True)
+            let expected = Just (In.Boolean True)
                 actual = coerceVariableValue
                     (ScalarInputType boolean) (Aeson.Bool True)
              in actual `shouldBe` expected
         it "coerces zero to an integer" $
-            let expected = Just (Int 0)
+            let expected = Just (In.Int 0)
                 actual = coerceVariableValue
                     (ScalarInputType int) (Aeson.Number 0)
              in actual `shouldBe` expected
@@ -65,24 +66,24 @@ spec = do
                     (ScalarInputType int) (Aeson.Number $ scientific 14 (-1))
              in actual `shouldSatisfy` isNothing
         it "coerces float numbers" $
-            let expected = Just (Float 1.4)
+            let expected = Just (In.Float 1.4)
                 actual = coerceVariableValue
                     (ScalarInputType float) (Aeson.Number $ scientific 14 (-1))
              in actual `shouldBe` expected
         it "coerces IDs" $
-            let expected = Just (String "1234")
+            let expected = Just (In.String "1234")
                 actual = coerceVariableValue
                     (ScalarInputType id) (Aeson.String "1234")
              in actual `shouldBe` expected
         it "coerces input objects" $
             let actual = coerceVariableValue singletonInputObject
                     $ Aeson.object ["field" .= ("asdf" :: Aeson.Value)]
-                expected = Just $ Object $ HashMap.singleton "field" "asdf"
+                expected = Just $ In.Object $ HashMap.singleton "field" "asdf"
              in actual `shouldBe` expected
         it "skips the field if it is missing in the variables" $
             let actual = coerceVariableValue
                     singletonInputObject Aeson.emptyObject
-                expected = Just $ Object HashMap.empty
+                expected = Just $ In.Object HashMap.empty
              in actual `shouldBe` expected
         it "fails if input object value contains extra fields" $
             let actual = coerceVariableValue singletonInputObject
@@ -94,25 +95,25 @@ spec = do
              in actual `shouldSatisfy` isNothing
         it "preserves null" $
             let actual = coerceVariableValue (ScalarInputType id) Aeson.Null
-             in actual `shouldBe` Just Null
+             in actual `shouldBe` Just In.Null
         it "preserves list order" $
             let list = Aeson.toJSONList ["asdf" :: Aeson.Value, "qwer"]
                 listType = (ListInputType $ ScalarInputType string)
                 actual = coerceVariableValue listType list
-                expected = Just $ List [String "asdf", String "qwer"]
+                expected = Just $ In.List [In.String "asdf", In.String "qwer"]
              in actual `shouldBe` expected
 
     describe "coerceInputLiterals" $ do
         it "coerces enums" $
-            let expected = Just (Enum "NORTH")
+            let expected = Just (In.Enum "NORTH")
                 actual = coerceInputLiteral
-                    (EnumInputType direction) (Enum "NORTH")
+                    (EnumInputType direction) (In.Enum "NORTH")
              in lookupActual actual `shouldBe` expected
         it "fails with non-existing enum value" $
             let actual = coerceInputLiteral
-                    (EnumInputType direction) (Enum "NORTH_EAST")
+                    (EnumInputType direction) (In.Enum "NORTH_EAST")
              in actual `shouldSatisfy` isNothing
         it "coerces integers to IDs" $
-            let expected = Just (String "1234")
-                actual = coerceInputLiteral (ScalarInputType id) (Int 1234)
+            let expected = Just (In.String "1234")
+                actual = coerceInputLiteral (ScalarInputType id) (In.Int 1234)
              in lookupActual actual `shouldBe` expected
diff --git a/tests/Language/GraphQL/SchemaSpec.hs b/tests/Language/GraphQL/SchemaSpec.hs
index a5d37c0..9bc5530 100644
--- a/tests/Language/GraphQL/SchemaSpec.hs
+++ b/tests/Language/GraphQL/SchemaSpec.hs
@@ -10,16 +10,15 @@ import qualified Data.Sequence as Sequence
 import Language.GraphQL.AST.Core
 import Language.GraphQL.Error
 import Language.GraphQL.Schema
-import qualified Language.GraphQL.Type as Type
-import Language.GraphQL.Type.Definition
+import qualified Language.GraphQL.Type.Out as Out
 import Test.Hspec (Spec, describe, it, shouldBe)
 
 spec :: Spec
 spec =
     describe "resolve" $
         it "ignores invalid __typename" $ do
-            let resolver = NestingResolver $ pure $ object
-                    [ wrappedObject "field" $ pure $ Type.S "T"
+            let resolver = pure $ object
+                    [ Resolver "field" $ pure $ Out.String "T"
                     ]
                 schema = HashMap.singleton "__typename" resolver
                 fields = Sequence.singleton
diff --git a/tests/Language/GraphQL/Type/OutSpec.hs b/tests/Language/GraphQL/Type/OutSpec.hs
new file mode 100644
index 0000000..48b7fa4
--- /dev/null
+++ b/tests/Language/GraphQL/Type/OutSpec.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Language.GraphQL.Type.OutSpec
+    ( spec
+    ) where
+
+import Data.Functor.Identity (Identity)
+import qualified Language.GraphQL.Type.Out as Out
+import Test.Hspec (Spec, describe, it, shouldBe)
+
+spec :: Spec
+spec =
+    describe "Value" $
+        it "supports overloaded strings" $
+            let string = "Goldstaub abblasen." :: (Out.Value Identity)
+             in string `shouldBe` Out.String "Goldstaub abblasen."
diff --git a/tests/Test/DirectiveSpec.hs b/tests/Test/DirectiveSpec.hs
index 74167c9..250ef6e 100644
--- a/tests/Test/DirectiveSpec.hs
+++ b/tests/Test/DirectiveSpec.hs
@@ -8,6 +8,7 @@ import Data.Aeson (Value(..), object, (.=))
 import qualified Data.HashMap.Strict as HashMap
 import Language.GraphQL
 import Language.GraphQL.Type.Definition
+import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.Type.Schema (Schema(..))
 import Test.Hspec (Spec, describe, it, shouldBe)
 import Text.RawString.QQ (r)
@@ -15,7 +16,7 @@ import Text.RawString.QQ (r)
 experimentalResolver :: Schema IO
 experimentalResolver = Schema { query = queryType, mutation = Nothing }
   where
-    resolver = ValueResolver $ pure $ Number 5
+    resolver = pure $ Out.Int 5
     queryType = ObjectType "Query" Nothing
         $ HashMap.singleton "experimentalField"
         $ Field Nothing (ScalarOutputType int) mempty resolver
diff --git a/tests/Test/FragmentSpec.hs b/tests/Test/FragmentSpec.hs
index 1616865..5ebecab 100644
--- a/tests/Test/FragmentSpec.hs
+++ b/tests/Test/FragmentSpec.hs
@@ -9,7 +9,9 @@ import qualified Data.HashMap.Strict as HashMap
 import Data.Text (Text)
 import Language.GraphQL
 import qualified Language.GraphQL.Schema as Schema
-import qualified Language.GraphQL.Type as Type
+import Language.GraphQL.Type.Definition
+import qualified Language.GraphQL.Type.Out as Out
+import Language.GraphQL.Type.Schema
 import Test.Hspec
     ( Spec
     , describe
@@ -17,21 +19,19 @@ import Test.Hspec
     , shouldBe
     , shouldNotSatisfy
     )
-import Language.GraphQL.Type.Definition
-import Language.GraphQL.Type.Schema
 import Text.RawString.QQ (r)
 
 size :: Schema.Resolver IO
-size = Schema.wrappedObject "size" $ pure $ Type.S "L"
+size = Schema.Resolver "size" $ pure $ Out.String "L"
 
 circumference :: Schema.Resolver IO
-circumference = Schema.wrappedObject "circumference" $ pure $ Type.I 60
+circumference = Schema.Resolver "circumference" $ pure $ Out.Int 60
 
 garment :: Text -> Schema.Resolver IO
-garment typeName = Schema.wrappedObject "garment"
+garment typeName = Schema.Resolver "garment"
     $ pure $ Schema.object
     [ if typeName == "Hat" then circumference else size
-    , Schema.wrappedObject "__typename" $ pure $ Type.S typeName
+    , Schema.Resolver "__typename" $ pure $ Out.String typeName
     ]
 
 inlineQuery :: Text
@@ -107,7 +107,7 @@ spec = do
                 }
               }
             }|]
-                resolvers = Schema.wrappedObject "garment"
+                resolvers = Schema.Resolver "garment"
                     $ pure $ Schema.object [circumference,  size]
 
             actual <- graphql (toSchema resolvers) sourceQuery
diff --git a/tests/Test/RootOperationSpec.hs b/tests/Test/RootOperationSpec.hs
index 935b96d..7e20e64 100644
--- a/tests/Test/RootOperationSpec.hs
+++ b/tests/Test/RootOperationSpec.hs
@@ -11,8 +11,8 @@ import qualified Language.GraphQL.Schema as Schema
 import Test.Hspec (Spec, describe, it, shouldBe)
 import Text.RawString.QQ (r)
 import Language.GraphQL.Type.Definition
+import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.Type.Schema
-import qualified Language.GraphQL.Type as Type
 
 hatType :: ObjectType IO
 hatType = ObjectType "Hat" Nothing
@@ -20,20 +20,19 @@ hatType = ObjectType "Hat" Nothing
     $ Field Nothing (ScalarOutputType int) mempty resolve
   where
     (Schema.Resolver resolverName resolve) =
-        Schema.wrappedObject "circumference" $ pure $ Type.I 60
+        Schema.Resolver "circumference" $ pure $ Out.Int 60
 
 schema :: Schema IO
 schema = Schema
     (ObjectType "Query" Nothing hatField)
     (Just $ ObjectType "Mutation" Nothing incrementField)
   where
-    garment = NestingResolver
-        $ pure $ Schema.object
-        [ Schema.wrappedObject "circumference" $ pure $ Type.I 60
+    garment = pure $ Schema.object
+        [ Schema.Resolver "circumference" $ pure $ Out.Int 60
         ]
     incrementField = HashMap.singleton "incrementCircumference"
         $ Field Nothing (ScalarOutputType int) mempty
-        $ NestingResolver $ pure $ Type.I 61
+        $ pure $ Out.Int 61
     hatField = HashMap.singleton "garment"
         $ Field Nothing (ObjectOutputType hatType) mempty garment
 
diff --git a/tests/Test/StarWars/Schema.hs b/tests/Test/StarWars/Schema.hs
index 5e702e0..993672c 100644
--- a/tests/Test/StarWars/Schema.hs
+++ b/tests/Test/StarWars/Schema.hs
@@ -15,7 +15,8 @@ import Data.Maybe (catMaybes)
 import qualified Language.GraphQL.Schema as Schema
 import Language.GraphQL.Trans
 import Language.GraphQL.Type.Definition
-import qualified Language.GraphQL.Type as Type
+import qualified Language.GraphQL.Type.In as In
+import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.Type.Schema
 import Test.StarWars.Data
 
@@ -30,45 +31,45 @@ schema = Schema { query = queryType, mutation = Nothing }
         , ("droid", Field Nothing (ScalarOutputType string) mempty droid)
         ]
 
-hero :: FieldResolver Identity
-hero = NestingResolver $ do
+hero :: ActionT Identity (Out.Value Identity)
+hero = do
   episode <- argument "episode"
   pure $ character $ case episode of
-      Schema.Enum "NEWHOPE" -> getHero 4
-      Schema.Enum "EMPIRE" -> getHero 5
-      Schema.Enum "JEDI" -> getHero 6
+      In.Enum "NEWHOPE" -> getHero 4
+      In.Enum "EMPIRE" -> getHero 5
+      In.Enum "JEDI" -> getHero 6
       _ -> artoo
 
-human :: FieldResolver Identity
-human = NestingResolver $ do
+human :: ActionT Identity (Out.Value Identity)
+human = do
     id' <- argument "id"
     case id' of
-        Schema.String i -> do
+        In.String i -> do
             humanCharacter <- lift $ return $ getHuman i >>= Just
             case humanCharacter of
-                Nothing -> pure Type.Null
+                Nothing -> pure Out.Null
                 Just e -> pure $ character e
         _ -> ActionT $ throwE "Invalid arguments."
 
-droid :: FieldResolver Identity
-droid = NestingResolver $ do
+droid :: ActionT Identity (Out.Value Identity)
+droid = do
     id' <- argument "id"
     case id' of
-        Schema.String i -> getDroid i >>= pure . character
+        In.String i -> getDroid i >>= pure . character
         _ -> ActionT $ throwE "Invalid arguments."
 
-character :: Character -> Type.Wrapping (FieldResolver Identity)
+character :: Character -> Out.Value Identity
 character char = Schema.object
-    [ Schema.wrappedObject "id" $ pure $ Type.S $ id_ char
-    , Schema.wrappedObject "name" $ pure $ Type.S $ name_ char
-    , Schema.wrappedObject "friends"
-        $ pure
-        $ Type.List
-        $ fmap character
-        $ getFriends char
-    , Schema.wrappedObject "appearsIn" $ pure
-        $ Type.List $ Type.E <$> catMaybes (getEpisode <$> appearsIn char)
-    , Schema.wrappedObject "secretBackstory" $ Type.S <$> secretBackstory char
-    , Schema.wrappedObject "homePlanet" $ pure $ Type.S $ either mempty homePlanet char
-    , Schema.wrappedObject "__typename" $ pure $ Type.S $ typeName char
+    [ Schema.Resolver "id" $ pure $ Out.String $ id_ char
+    , Schema.Resolver "name" $ pure $ Out.String $ name_ char
+    , Schema.Resolver "friends"
+        $ pure $ Out.List $ fmap character $ getFriends char
+    , Schema.Resolver "appearsIn" $ pure
+        $ Out.List $ Out.Enum <$> catMaybes (getEpisode <$> appearsIn char)
+    , Schema.Resolver "secretBackstory" $ Out.String
+        <$> secretBackstory char
+    , Schema.Resolver "homePlanet" $ pure $ Out.String
+        $ either mempty homePlanet char
+    , Schema.Resolver "__typename" $ pure $ Out.String
+        $ typeName char
     ]