@@ -51,7 +51,7 @@ newtype Context a = Context
52--------------------------------------------------------------------------------
52--------------------------------------------------------------------------------
53instance Monoid (Context a) where
53instance Monoid (Context a) where
54− mempty = Context $ \_ _ -> empty
54+ mempty = missingField
55 mappend (Context f) (Context g) = Context $ \k i -> f k i <|> g k i
55 mappend (Context f) (Context g) = Context $ \k i -> f k i <|> g k i