Derive Traversable for Value (#414)

* Derive Traversable for Value

* changelog, cabal

changelog.md

@@ -1,3 +1,9 @@
+3.5.14.0 (unreleased)
+========
+- @parsonsmatt
+    - [#414](https://github.com/bitemyapp/esqueleto/pull/414)
+        - Derive `Foldable` and `Traversable` for `Value`.
+
 3.5.13.2
 ========
 - @blujupiter32

esqueleto.cabal

@@ -2,7 +2,7 @@ cabal-version: 1.12
 
 name:           esqueleto
 
-version:        3.5.13.2
+version:        3.5.14.0
 synopsis:       Type-safe EDSL for SQL queries on persistent backends.
 description:    @esqueleto@ is a bare bones, type-safe EDSL for SQL queries that works with unmodified @persistent@ SQL backends.  Its language closely resembles SQL, so you don't have to learn new concepts, just new syntax, and it's fairly easy to predict the generated SQL and optimize it for your backend. Most kinds of errors committed when writing SQL are caught as compile-time errors---although it is possible to write type-checked @esqueleto@ queries that fail at runtime.
                 .

src/Database/Esqueleto/Internal/Internal.hs

@@ -6,6 +6,7 @@
 
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE EmptyDataDecls #-}
 {-# LANGUAGE FlexibleContexts #-}
@@ -1270,11 +1271,8 @@ else_ = id
 
 -- | A single value (as opposed to a whole entity).  You may use
 -- @('^.')@ or @('?.')@ to get a 'Value' from an 'Entity'.
-newtype Value a = Value { unValue :: a } deriving (Eq, Ord, Show, Typeable)
-
--- | @since 1.4.4
-instance Functor Value where
-    fmap f (Value a) = Value (f a)
+newtype Value a = Value { unValue :: a }
+    deriving (Eq, Ord, Show, Typeable, Functor, Foldable, Traversable)
 
 instance Applicative Value where
   (<*>) (Value f) (Value a) = Value (f a)