Common.hs: implement wordReader using Parsec

cardano-cli/src/Cardano/CLI/EraBased/Options/Common.hs

@@ -45,7 +45,7 @@ import           Data.Time.Clock (UTCTime)
 import           Data.Time.Format (defaultTimeLocale, parseTimeOrError)
 import           Data.Word
 import           GHC.Exts (IsList (..))
-import           GHC.Natural (Natural, naturalToWordMaybe)
+import           GHC.Natural (Natural)
 import           Network.Socket (PortNumber)
 import           Options.Applicative hiding (help, str)
 import qualified Options.Applicative as Opt
@@ -3188,14 +3188,14 @@ pMaxTransactionSize =
 -- to avoid the overflow issues of 'Opt.auto' described in https://github.com/IntersectMBO/cardano-cli/issues/860.
 wordReader :: forall a. (Typeable a, Integral a, Bits a) => ReadM a
 wordReader =
-  Opt.eitherReader parser
+  readerFromParsecParser parsecParser
  where
-  parser s =
-    case readMaybe s >>= naturalToWordMaybe >>= toIntegralSized of
-      Nothing ->
-        Left $ "Cannot parse " <> s <> " as a " <> typeName
-      Just a ->
-        Right a
+  parsecParser :: Parsec.Parser a
+  parsecParser = do
+    i <- decimal
+    case toIntegralSized i of
+      Nothing -> fail $ "Cannot parse " <> show i <> " as a " <> typeName
+      Just n -> return n
   typeName = show $ typeRep (Proxy @a)
 
 pMaxBlockHeaderSize :: Parser Word16