[chore] make specialisation possible for ghc and some minor style

improvements

src/Nixfmt.hs

@@ -3,7 +3,6 @@
 module Nixfmt (
   errorBundlePretty,
   ParseErrorBundle,
-  Width,
   format,
   formatVerify,
   printAst,
@@ -22,9 +21,6 @@ import qualified Text.Megaparsec as Megaparsec (parse)
 import Text.Megaparsec.Error (errorBundlePretty)
 import Text.Pretty.Simple (pShow)
 
--- import Debug.Trace (traceShow, traceShowId)
-
-type Width = Int
 type Layouter = forall a. (Pretty a, LanguageElement a) => a -> Text
 
 -- | @format w filename source@ returns either a parsing error specifying a
@@ -36,7 +32,7 @@ format layout filename =
     . Megaparsec.parse Parser.file filename
 
 -- | Pretty print the internal AST for debugging
-printAst :: FilePath -> Text -> Either String Text
+printAst :: FilePath -> Text -> Either String a
 printAst path unformatted = do
   Whole unformattedParsed' _ <- first errorBundlePretty . Megaparsec.parse Parser.file path $ unformatted
   Left (unpack $ toStrict $ pShow unformattedParsed')

src/Nixfmt/Lexer.hs

@@ -179,6 +179,7 @@ takeTrivia = get <* put []
 
 pushTrivia :: (MonadState Trivia m) => Trivia -> m ()
 pushTrivia t = modify (<> t)
+{-# INLINEABLE pushTrivia #-}
 
 lexeme :: Parser a -> Parser (Ann a)
 lexeme p = do

src/Nixfmt/Parser.hs

@@ -3,6 +3,7 @@
 
 module Nixfmt.Parser where
 
+import Control.Applicative (liftA2)
 import Control.Monad (guard, liftM2)
 import Control.Monad.Combinators (sepBy)
 import qualified Control.Monad.Combinators.Expr as MPExpr (
@@ -128,10 +129,7 @@ slash :: Parser Text
 slash = chunk "/" <* notFollowedBy (char '/')
 
 instance (Semigroup a) => Semigroup (Parser a) where
-  fx <> fy = do
-    x <- fx
-    y <- fy
-    pure $ x <> y
+  (<>) = liftA2 (<>)
 
 envPath :: Parser (Ann Token)
 envPath =

src/Nixfmt/Types.hs

@@ -109,11 +109,7 @@ ann l v =
 -- | Equality of annotated syntax is defined as equality of their corresponding
 -- semantics, thus ignoring the annotations.
 instance (Eq a) => Eq (Ann a) where
-  Ann{value = x} == Ann{value = y} = x == y
-
--- Trivia is ignored for Eq, so also don't show
--- instance Show a => Show (Ann a) where
---    show (Ann _ a _) = show a
+  (==) = (==) `on` value
 
 data Item a
   = -- | An item

src/Nixfmt/Util.hs

@@ -49,18 +49,22 @@ uriChar = charClass "~!@$%&*-=_+:',./?"
 -- | Match one or more characters that match a predicate.
 someP :: (MonadParsec e s m) => (Token s -> Bool) -> m (Tokens s)
 someP = takeWhile1P Nothing
+{-# INLINEABLE someP #-}
 
 -- | Match zero or more characters that match a predicate.
 manyP :: (MonadParsec e s m) => (Token s -> Bool) -> m (Tokens s)
 manyP = takeWhileP Nothing
+{-# INLINEABLE manyP #-}
 
 -- | Match one or more texts and return the concatenation.
 someText :: (MonadParsec e s m) => m Text -> m Text
 someText p = Text.concat <$> some p
+{-# INLINEABLE someText #-}
 
 -- | Match zero or more texts and return the concatenation.
 manyText :: (MonadParsec e s m) => m Text -> m Text
 manyText p = Text.concat <$> many p
+{-# INLINEABLE manyText #-}
 
 -- | The longest common prefix of the arguments.
 commonPrefix :: Text -> Text -> Text