Add Functor and Bifunctor instances for (:&)

Author: isomorpheme

changelog.md

@@ -1,3 +1,9 @@
+3.5.11.3
+========
+- @isomorpheme
+    - [#393](https://github.com/bitemyapp/esqueleto/pull/393)
+        - Add Functor and Bifunctor instances for `(:&)`
+
 3.5.11.2
 ========
 - @arguri

esqueleto.cabal

@@ -2,7 +2,7 @@ cabal-version: 1.12
 
 name:           esqueleto
 
-version:        3.5.11.2
+version:        3.5.11.3
 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

@@ -52,6 +52,7 @@ import Data.Semigroup
 import qualified Control.Monad.Trans.Reader as R
 import qualified Control.Monad.Trans.State as S
 import qualified Control.Monad.Trans.Writer as W
+import Data.Bifunctor (Bifunctor(..))
 import qualified Data.ByteString as B
 import Data.Coerce (coerce)
 import qualified Data.Conduit as C
@@ -1442,6 +1443,14 @@ data (:&) a b = a :& b
     deriving (Eq, Show)
 infixl 2 :&
 
+-- | @since 3.5.11.3
+instance Functor (:&) where
+  fmap = bimap id
+
+-- | @since 3.5.11.3
+instance Bifunctor (:&) where
+  bimap f g (x :& y) = f x :& g y
+
 -- | Different kinds of locking clauses supported by 'locking'.
 --
 -- Note that each RDBMS has different locking support.  The