Put operators after other names

Previously ‘RdrName’s were sorted by simple comparison of their names.
However, in ASCII not all “operator-like” symbols go after alpha-numeric
characters. This resulted in this sort of output:

  import Linear.Vector ((*^), Additive (..), (^*))

The new ordering scheme allows us to separate operators and other names:

  import Linear.Vector (Additive (..), (*^), (^*))

CHANGELOG.md

@@ -7,6 +7,9 @@
   disabled part is still syntactically correct. [Issue
   601](https://github.com/tweag/ormolu/issues/601).
 
+* Improved sorting of operators in imports. [Issue
+  602](https://github.com/tweag/ormolu/issues/602).
+
 ## Ormolu 0.1.0.0
 
 * Fixed rendering of type signatures concerning several identifiers. [Issue

data/examples/import/explicit-imports-out.hs

@@ -1,12 +1,12 @@
 import qualified MegaModule as M
-  ( (<<<),
-    (>>>),
-    Either,
+  ( Either,
     Maybe (Just, Nothing),
     MaybeT (..),
-    Monad ((>>), (>>=), return),
+    Monad (return, (>>), (>>=)),
     MonadBaseControl,
     join,
     liftIO,
     void,
+    (<<<),
+    (>>>),
   )

data/examples/import/explicit-imports-with-comments-out.hs

@@ -1,6 +1,7 @@
 import qualified MegaModule as M
   ( -- (1)
-    (<<<), -- (2)
-    (>>>),
+    -- (2)
     Either, -- (3)
+    (<<<),
+    (>>>),
   )

data/examples/import/nested-explicit-imports-out.hs

@@ -1,10 +1,10 @@
 import qualified MegaModule as M
-  ( (<<<),
-    (>>>),
-    Either,
+  ( Either,
     Monad
-      ( (>>),
-        (>>=),
-        return
+      ( return,
+        (>>),
+        (>>=)
       ),
+    (<<<),
+    (>>>),
   )

data/examples/import/qualified-prelude-out.hs

@@ -1,4 +1,4 @@
 module P where
 
 import qualified Prelude
-import Prelude hiding ((.), id)
+import Prelude hiding (id, (.))

data/examples/import/sorted-export-list-out.hs

@@ -0,0 +1 @@
+import Linear.Vector (Additive (..), (*^), (^*))

data/examples/import/sorted-export-list.hs

@@ -0,0 +1 @@
+import Linear.Vector (Additive (..), (*^), (^*))

src/Ormolu/Imports.hs

@@ -9,13 +9,14 @@ module Ormolu.Imports
 where
 
 import Data.Bifunctor
+import Data.Char (isAlphaNum)
 import Data.Function (on)
 import Data.Generics (gcompare)
 import Data.List (nubBy, sortBy)
 import GHC hiding (GhcPs, IE)
 import GHC.Hs.Extension
 import GHC.Hs.ImpExp (IE (..))
-import Ormolu.Utils (notImplemented)
+import Ormolu.Utils (notImplemented, showOutputable)
 
 -- | Sort imports by module name. This also sorts explicit import lists for
 -- each declaration.
@@ -77,12 +78,27 @@ getIewn = \case
 
 -- | Compare two @'IEWrapppedName' 'RdrName'@ things.
 compareIewn :: IEWrappedName RdrName -> IEWrappedName RdrName -> Ordering
-compareIewn (IEName x) (IEName y) = unLoc x `compare` unLoc y
+compareIewn (IEName x) (IEName y) = unLoc x `compareRdrName` unLoc y
 compareIewn (IEName _) (IEPattern _) = LT
 compareIewn (IEName _) (IEType _) = LT
 compareIewn (IEPattern _) (IEName _) = GT
-compareIewn (IEPattern x) (IEPattern y) = unLoc x `compare` unLoc y
+compareIewn (IEPattern x) (IEPattern y) = unLoc x `compareRdrName` unLoc y
 compareIewn (IEPattern _) (IEType _) = LT
 compareIewn (IEType _) (IEName _) = GT
 compareIewn (IEType _) (IEPattern _) = GT
-compareIewn (IEType x) (IEType y) = unLoc x `compare` unLoc y
+compareIewn (IEType x) (IEType y) = unLoc x `compareRdrName` unLoc y
+
+compareRdrName :: RdrName -> RdrName -> Ordering
+compareRdrName x y =
+  case (getNameStr x, getNameStr y) of
+    ([], []) -> EQ
+    ((_ : _), []) -> GT
+    ([], (_ : _)) -> LT
+    ((x' : _), (y' : _)) ->
+      case (isAlphaNum x', isAlphaNum y') of
+        (False, False) -> x `compare` y
+        (True, False) -> LT
+        (False, True) -> GT
+        (True, True) -> x `compare` y
+  where
+    getNameStr = showOutputable . rdrNameOcc

src/Ormolu/Printer/Meat/Declaration.hs

@@ -12,7 +12,7 @@ module Ormolu.Printer.Meat.Declaration
 where
 
 import Data.List (sort)
-import Data.List.NonEmpty ((<|), NonEmpty (..))
+import Data.List.NonEmpty (NonEmpty (..), (<|))
 import qualified Data.List.NonEmpty as NE
 import GHC hiding (InlinePragma)
 import OccName (occNameFS)

src/Ormolu/Printer/Meat/Declaration/Value.hs

@@ -21,7 +21,7 @@ import Data.Char (isPunctuation, isSymbol)
 import Data.Data hiding (Infix, Prefix)
 import Data.Functor ((<&>))
 import Data.List (intersperse, sortOn)
-import Data.List.NonEmpty ((<|), NonEmpty (..))
+import Data.List.NonEmpty (NonEmpty (..), (<|))
 import qualified Data.List.NonEmpty as NE
 import Data.Text (Text)
 import qualified Data.Text as Text