T.P.Shared: Remove ToString, ToText typeclasses [API change].

T.P.Parsing: revise type of readWithM so that it takes a Text
rather than a polymorphic ToText value.

These typeclasses were there to ease the transition from String
to Text. They are no longer needed, and they may clash with
more useful versions under the same name.

This will require a bump to 2.13.

src/Text/Pandoc/Parsing.hs

@@ -1128,13 +1128,13 @@ gridTableFooter = optional blanklines
 ---
 
 -- | Removes the ParsecT layer from the monad transformer stack
-readWithM :: (Stream s m Char, ToText s)
-          => ParserT s st m a    -- ^ parser
+readWithM :: Monad m
+          => ParserT Text st m a -- ^ parser
           -> st                  -- ^ initial state
-          -> s                   -- ^ input
+          -> Text                -- ^ input
           -> m (Either PandocError a)
 readWithM parser state input =
-    mapLeft (PandocParsecError $ toText input) `liftM` runParserT parser state "source" input
+    mapLeft (PandocParsecError input) <$> runParserT parser state "source" input
 
 -- | Parse a string with a given parser and state
 readWith :: Parser Text st a

src/Text/Pandoc/Shared.hs

@@ -25,8 +25,6 @@ module Text.Pandoc.Shared (
                      ordNub,
                      findM,
                      -- * Text processing
-                     ToString (..),
-                     ToText (..),
                      tshow,
                      backslashEscapes,
                      escapeStringUsing,
@@ -183,24 +181,6 @@ findM p = foldr go (pure Nothing)
 -- Text processing
 --
 
-class ToString a where
-  toString :: a -> String
-
-instance ToString String where
-  toString = id
-
-instance ToString T.Text where
-  toString = T.unpack
-
-class ToText a where
-  toText :: a -> T.Text
-
-instance ToText String where
-  toText = T.pack
-
-instance ToText T.Text where
-  toText = id
-
 tshow :: Show a => a -> T.Text
 tshow = T.pack . show