Add putErrLn to match putStrLn (#67)

* Add `putErrLn` to match `putStrLn`

Fix #66

* Add putErr for the most usual inference case

* Rename `putErr` into `putErrText`

In order to allow further specializations in the future if necessary.

src/Protolude/Show.hs

@@ -8,6 +8,7 @@
 module Protolude.Show (
   Print(..),
   putText,
+  putErrText,
   putLText,
   putByteString,
   putLByteString,
@@ -27,7 +28,7 @@ import qualified Data.Text.IO as T
 import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.IO as TL
 
-import System.IO (Handle, stdout)
+import System.IO (Handle, stdout, stderr)
 
 
 class Print a where
@@ -37,6 +38,8 @@ class Print a where
   hPutStrLn :: MonadIO m => Handle -> a -> m ()
   putStrLn :: MonadIO m => a -> m ()
   putStrLn = hPutStrLn stdout
+  putErrLn ::  MonadIO m => a -> m ()
+  putErrLn = hPutStrLn stderr
 
 instance Print T.Text where
   hPutStr = \h -> liftIO . T.hPutStr h
@@ -74,3 +77,7 @@ putByteString = putStrLn
 putLByteString :: MonadIO m => BL.ByteString -> m ()
 putLByteString = putStrLn
 {-# SPECIALIZE putLByteString :: BL.ByteString -> Base.IO () #-}
+
+putErrText :: MonadIO m => T.Text -> m ()
+putErrText = putErrLn
+{-# SPECIALIZE putErrText :: T.Text -> Base.IO () #-}