From 4ef3604a651e62e217da205129298d034e541f48 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Thu, 11 May 2017 14:19:34 -0400
Subject: [PATCH] Revert "Revert "Define a Crosswalk instance for Patch.""

This reverts commit 20d96850fa7ee2b1ad3c949b128186eaa8f22f6b.
---
 src/Patch.hs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Patch.hs b/src/Patch.hs
index 9c212d11c..402783dbc 100644
--- a/src/Patch.hs
+++ b/src/Patch.hs
@@ -16,6 +16,7 @@ module Patch
 , patchType
 ) where
 
+import Data.Align
 import Data.Functor.Listable
 import Data.These
 import Prologue
@@ -90,3 +91,8 @@ instance Listable1 Patch where
 
 instance Listable a => Listable (Patch a) where
   tiers = tiers1
+
+instance Crosswalk Patch where
+  crosswalk f (Replace a b) = alignWith (these Delete Insert Replace) (f a) (f b)
+  crosswalk f (Insert b) = Insert <$> f b
+  crosswalk f (Delete a) = Delete <$> f a