Introduce a stringParts helper

Author: layus

src/Nix/Eval.hs

@@ -465,14 +465,9 @@ assembleString
    . (MonadEval v m, FromValue NixString m v)
   => NString (m v)
   -> m (Maybe NixString)
-assembleString =
-  fromParts .
-    \case
-      Indented   _ parts -> parts
-      DoubleQuoted parts -> parts
+assembleString = fromParts . stringParts
  where
   fromParts xs = (mconcat <$>) . sequence <$> traverse go xs
-
   go =
     runAntiquoted
       "\n"

src/Nix/Expr/Types.hs

@@ -610,6 +610,10 @@ paramName :: Params r -> Maybe VarName
 paramName (Param n       ) = pure n
 paramName (ParamSet _ _ n) = n
 
+stringParts :: NString r -> [Antiquoted Text r]
+stringParts (DoubleQuoted parts) = parts
+stringParts (Indented _   parts) = parts
+
 stripPositionInfo :: NExpr -> NExpr
 stripPositionInfo = transport phi
  where