ghcide: Core.Compile: spliceExpression: rm harmful DList conversion

DList tells:
https://hackage.haskell.org/package/dlist-1.0/docs/src/Data.DList.Internal.html#fromList

Author: Anton-Latukha

ghcide/src/Development/IDE/Core/Compile.hs

@@ -76,7 +76,6 @@ import           Control.Monad.Extra
 import           Control.Monad.Trans.Except
 import           Data.Bifunctor                    (second)
 import qualified Data.ByteString                   as BS
-import qualified Data.DList                        as DL
 import           Data.IORef
 import           Data.List.Extra
 import qualified Data.Map.Strict                   as Map
@@ -99,6 +98,7 @@ import           Data.Binary
 import           Data.Coerce
 import           Data.Functor
 import qualified Data.HashMap.Strict               as HashMap
+import           Data.Foldable                     (fold)
 import           Data.Tuple.Extra                  (dupe)
 import           Data.Either.Extra                 (maybeToEither)
 import           Data.Unique                       as Unique
@@ -469,13 +469,13 @@ generateHieAsts hscEnv tcm =
 
 spliceExpresions :: Splices -> [LHsExpr GhcTc]
 spliceExpresions Splices{..} =
-    DL.toList $ mconcat
-        [ DL.fromList $ map fst exprSplices
-        , DL.fromList $ map fst patSplices
-        , DL.fromList $ map fst typeSplices
-        , DL.fromList $ map fst declSplices
-        , DL.fromList $ map fst awSplices
-        ]
+  fold
+    [ map fst exprSplices
+    , map fst patSplices
+    , map fst typeSplices
+    , map fst declSplices
+    , map fst awSplices
+    ]
 
 -- | In addition to indexing the `.hie` file, this function is responsible for
 -- maintaining the 'IndexQueue' state and notfiying the user about indexing