From d260ea19c9d5bd4c8c236225f79a082ea4aaf7dd Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Sun, 18 Sep 2016 09:54:07 +0900
Subject: [PATCH] Add a Semigroup instance over Source.

---
 src/Source.hs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Source.hs b/src/Source.hs
index 9dc50df45..04cc5f379 100644
--- a/src/Source.hs
+++ b/src/Source.hs
@@ -100,6 +100,9 @@ sourceSpanToRange source SourceSpan{..} = Range start end
         sumLengths = sum . fmap (\ Range{..} -> end - start)
 
 
+instance Semigroup (Source a) where
+  Source a <> Source b = Source (a Vector.++ b)
+
 instance Monoid (Source a) where
   mempty = fromList []
-  mappend = (Source .) . (Vector.++) `on` getVector
+  mappend = (<>)