Merge pull request #513 from treeowl/newtype-since

Make parser state a newtype

haddock-library/src/Documentation/Haddock/Parser/Monad.hs

@@ -42,7 +42,7 @@ import           Data.Tuple
 
 import           Documentation.Haddock.Types (Version)
 
-data ParserState = ParserState {
+newtype ParserState = ParserState {
   parserStateSince :: Maybe Version
 } deriving (Eq, Show)