From 0aa3c23a756339acac8258de91c9ea44232e4ccc Mon Sep 17 00:00:00 2001
From: Felipe Lessa <felipe.lessa@gmail.com>
Date: Sun, 9 Sep 2012 09:47:38 -0300
Subject: [PATCH] New SqlEntity constraint synonym.

---
 src/Database/Esqueleto.hs              | 1 +
 src/Database/Esqueleto/Internal/Sql.hs | 9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/Database/Esqueleto.hs b/src/Database/Esqueleto.hs
index 5c441c1..07db494 100644
--- a/src/Database/Esqueleto.hs
+++ b/src/Database/Esqueleto.hs
@@ -38,6 +38,7 @@ module Database.Esqueleto
     -- * SQL backend
   , SqlQuery
   , SqlExpr
+  , SqlEntity
   , select
   , selectDistinct
   , selectSource
diff --git a/src/Database/Esqueleto/Internal/Sql.hs b/src/Database/Esqueleto/Internal/Sql.hs
index 56c3244..bc40553 100644
--- a/src/Database/Esqueleto/Internal/Sql.hs
+++ b/src/Database/Esqueleto/Internal/Sql.hs
@@ -14,6 +14,7 @@ module Database.Esqueleto.Internal.Sql
   ( -- * The pretty face
     SqlQuery
   , SqlExpr
+  , SqlEntity
   , select
   , selectSource
   , selectDistinct
@@ -74,6 +75,11 @@ instance Applicative SqlQuery where
   (<*>) = ap
 
 
+-- | Constraint synonym for @persistent@ entities whose backend
+-- is 'SqlPersist'.
+type SqlEntity ent = (PersistEntity ent, PersistEntityBackend ent ~ SqlPersist)
+
+
 ----------------------------------------------------------------------
 
 
@@ -498,8 +504,7 @@ delete = rawExecute DELETE
 -- @
 update :: ( MonadLogger m
           , MonadResourceBase m
-          , PersistEntity val
-          , PersistEntityBackend val ~ SqlPersist )
+          , SqlEntity val )
        => (SqlExpr (Entity val) -> SqlQuery ())
        -> SqlPersist m ()
 update = rawExecute UPDATE . from