Custom Show for Range and Span

src/Data/Range.hs

@@ -17,7 +17,7 @@ import Proto3.Wire.Decode as Decode
 
 -- | A half-open interval of integers, defined by start & end indices.
 data Range = Range { start :: {-# UNPACK #-} !Int, end :: {-# UNPACK #-} !Int }
-  deriving (Eq, Show, Generic, Named)
+  deriving (Eq, Generic, Named)
 
 emptyRange :: Range
 emptyRange = Range 0 0
@@ -53,6 +53,9 @@ instance Semigroup Range where
 instance Ord Range where
   a <= b = start a <= start b
 
+instance Show Range where
+  showsPrec _ Range{..} = showChar '[' . shows start . showString " - " . shows end . showChar ']'
+
 instance ToJSONFields Range where
   toJSONFields Range{..} = ["sourceRange" .= [ start, end ]]
 

src/Data/Span.hs

@@ -24,18 +24,21 @@ data Pos = Pos
   { posLine   :: !Int
   , posColumn :: !Int
   }
-  deriving (Show, Read, Eq, Ord, Generic, Hashable)
+  deriving (Eq, Ord, Generic, Hashable)
 
 -- | A Span of position information
 data Span = Span
   { spanStart :: Pos
   , spanEnd   :: Pos
   }
-  deriving (Show, Read, Eq, Ord, Generic, Hashable, Named)
+  deriving (Eq, Ord, Generic, Hashable, Named)
 
 
 -- Instances
 
+instance Show Pos where
+  showsPrec _ Pos{..} = showChar '[' . shows posLine . showString ", " . shows posColumn . showChar ']'
+
 instance Named Pos where nameOf _ = "Position"
 instance Message Pos where
   encodeMessage _ Pos{..} = encodeMessageField 1 posLine <> encodeMessageField 2 posColumn
@@ -61,6 +64,9 @@ instance HasDefault Pos where
   def = lowerBound @Pos
 
 
+instance Show Span where
+  showsPrec _ Span{..} = shows spanStart . showString " - " . shows spanEnd
+
 instance Message Span where
   encodeMessage _ Span{..} = Encode.embedded 1 (encodeMessage 1 spanStart) <> Encode.embedded 2 (encodeMessage 1 spanEnd)
   decodeMessage _ = Span <$> embeddedAt (decodeMessage 1) 1 <*> embeddedAt (decodeMessage 1) 2