Tweak union.goDifferentHash (#277)

Author: sjakobi

Data/HashMap/Internal.hs

@@ -1635,7 +1635,7 @@ unionWithKey f = go 0
     leafHashCode _ = error "leafHashCode"
 
     goDifferentHash s h1 h2 t1 t2
-        | m1 == m2  = BitmapIndexed m1 (A.singleton $! go (s+bitsPerSubkey) t1 t2)
+        | m1 == m2  = BitmapIndexed m1 (A.singleton $! goDifferentHash (s+bitsPerSubkey) h1 h2 t1 t2)
         | m1 <  m2  = BitmapIndexed (m1 .|. m2) (A.pair t1 t2)
         | otherwise = BitmapIndexed (m1 .|. m2) (A.pair t2 t1)
       where

Data/HashMap/Internal/Strict.hs

@@ -507,7 +507,7 @@ unionWithKey f = go 0
     leafHashCode _ = error "leafHashCode"
 
     goDifferentHash s h1 h2 t1 t2
-        | m1 == m2  = BitmapIndexed m1 (A.singleton $! go (s+bitsPerSubkey) t1 t2)
+        | m1 == m2  = BitmapIndexed m1 (A.singleton $! goDifferentHash (s+bitsPerSubkey) h1 h2 t1 t2)
         | m1 <  m2  = BitmapIndexed (m1 .|. m2) (A.pair t1 t2)
         | otherwise = BitmapIndexed (m1 .|. m2) (A.pair t2 t1)
       where