treewide: use pattern AnnE, add doc to it

Author: Anton-Latukha

src/Nix/Cited/Basic.hs

@@ -16,7 +16,6 @@ import           Prelude                 hiding ( force )
 import           Control.Comonad                ( Comonad )
 import           Control.Comonad.Env            ( ComonadEnv )
 import           Control.Monad.Catch     hiding ( catchJust )
-import           Data.Fix
 import           Nix.Cited
 import           Nix.Eval                      as Eval
 import           Nix.Exec
@@ -64,13 +63,12 @@ instance ( Has e Options
 
         -- Gather the current evaluation context at the time of thunk
         -- creation, and record it along with the thunk.
-        let go (fromException ->
-                    Just (EvaluatingExpr scope
-                              (Fix (Compose (Ann s e))))) =
-                let e' = Compose (Ann s (Nothing <$ e))
-                in [Provenance scope e']
-            go _ = mempty
-            ps = concatMap (go . frame) frames
+        let
+          go (fromException -> Just (EvaluatingExpr scope (AnnE s e))) =
+            let e' = Compose (Ann s (Nothing <$ e)) in
+            [Provenance scope e']
+          go _ = mempty
+          ps = concatMap (go . frame) frames
 
         Cited . NCited ps <$> thunk mv
       )

src/Nix/Eval.hs

@@ -15,7 +15,6 @@ module Nix.Eval where
 import           Control.Monad                  ( foldM )
 import           Control.Monad.Fix              ( MonadFix )
 import           Data.Semialign.Indexed         ( ialignWith )
-import           Data.Fix                       ( Fix(Fix) )
 import qualified Data.HashMap.Lazy             as M
 import           Data.List                      ( partition )
 import           Data.These                     ( These(..) )
@@ -496,7 +495,7 @@ buildArgument params arg =
 
 addSourcePositions
   :: (MonadReader e m, Has e SrcSpan) => Transform NExprLocF (m a)
-addSourcePositions f v@(Fix (Compose (Ann ann _))) =
+addSourcePositions f v@(AnnE ann _) =
   local (set hasLens ann) $ f v
 
 addStackFrames

src/Nix/Expr/Types/Annotated.hs

@@ -84,6 +84,7 @@ data Ann ann a = Ann
 
 type AnnF ann f = Compose (Ann ann) f
 
+-- | Pattern: @Fix (Compose (Ann _ _))@.
 pattern AnnE
   :: forall ann (g :: * -> *)
   . ann

src/Nix/Reduce.hs

@@ -373,7 +373,7 @@ pruneTree opts =
         (reduceSets opts)  -- Reduce set members that aren't used; breaks if hasAttr is used
         binds
 
-    NLet binds (Just body@(Fix (Compose (Ann _ x)))) ->
+    NLet binds (Just body@(AnnE _ x)) ->
       pure $
         list
           x
@@ -384,8 +384,8 @@ pruneTree opts =
       pure $ NSelect aset (NE.map pruneKeyName attr) (join alt)
 
     -- These are the only short-circuiting binary operators
-    NBinary NAnd (Just (Fix (Compose (Ann _ larg)))) _ -> pure larg
-    NBinary NOr  (Just (Fix (Compose (Ann _ larg)))) _ -> pure larg
+    NBinary NAnd (Just (AnnE _ larg)) _ -> pure larg
+    NBinary NOr  (Just (AnnE _ larg)) _ -> pure larg
 
     -- If the function was never called, it means its argument was in a
     -- thunk that was forced elsewhere.
@@ -399,18 +399,18 @@ pruneTree opts =
     NBinary op (Just larg) Nothing -> pure $ NBinary op larg nNull
 
     -- If the scope of a with was never referenced, it's not needed
-    NWith Nothing (Just (Fix (Compose (Ann _ body)))) -> pure body
+    NWith Nothing (Just (AnnE _ body)) -> pure body
 
     NAssert Nothing _ ->
       fail "How can an assert be used, but its condition not?"
 
-    NAssert _ (Just (Fix (Compose (Ann _ body)))) -> pure body
+    NAssert _ (Just (AnnE _ body)) -> pure body
     NAssert (Just cond) _ -> pure $ NAssert cond nNull
 
     NIf Nothing _ _ -> fail "How can an if be used, but its condition not?"
 
-    NIf _ Nothing (Just (Fix (Compose (Ann _ f)))) -> pure f
-    NIf _ (Just (Fix (Compose (Ann _ t)))) Nothing -> pure t
+    NIf _ Nothing (Just (AnnE _ f)) -> pure f
+    NIf _ (Just (AnnE _ t)) Nothing -> pure t
 
     x                     -> sequence x
 

src/Nix/Render/Frame.hs

@@ -72,7 +72,7 @@ framePos
   -> Maybe SourcePos
 framePos (NixFrame _ f)
   | Just (e :: EvalFrame m v) <- fromException f = case e of
-    EvaluatingExpr _ (Fix (Compose (Ann (SrcSpan beg _) _))) -> pure beg
+    EvaluatingExpr _ (AnnE (SrcSpan beg _) _) -> pure beg
     _ -> Nothing
   | otherwise = Nothing
 
@@ -108,7 +108,7 @@ renderEvalFrame level f =
   do
     opts :: Options <- asks (view hasLens)
     case f of
-      EvaluatingExpr scope e@(Fix (Compose (Ann ann _))) ->
+      EvaluatingExpr scope e@(AnnE ann _) ->
         do
           let
             scopeInfo =
@@ -121,7 +121,7 @@ renderEvalFrame level f =
             $ renderLocation ann =<<
                 renderExpr level "While evaluating" "Expression" e
 
-      ForcingExpr _scope e@(Fix (Compose (Ann ann _))) | thunks opts ->
+      ForcingExpr _scope e@(AnnE ann _) | thunks opts ->
         fmap
           (: mempty)
           $ renderLocation ann =<<
@@ -135,7 +135,7 @@ renderEvalFrame level f =
 
       SynHole synfo ->
         sequence $
-          let e@(Fix (Compose (Ann ann _))) = _synHoleInfo_expr synfo in
+          let e@(AnnE ann _) = _synHoleInfo_expr synfo in
 
           [ renderLocation ann =<<
               renderExpr level "While evaluating" "Syntactic Hole" e
@@ -152,7 +152,7 @@ renderExpr
   -> Text
   -> NExprLoc
   -> m (Doc ann)
-renderExpr _level longLabel shortLabel e@(Fix (Compose (Ann _ x))) = do
+renderExpr _level longLabel shortLabel e@(AnnE _ x) = do
   opts :: Options <- asks (view hasLens)
   let rendered
           | verbose opts >= DebugInfo =