Improve/rename dropExcessTrailingPathSeparators

System/FilePath/Internal.hs

@@ -668,15 +668,12 @@ splitFileName_ fp
     = (dirSlash, file)
   where
     (dirSlash, file) = breakEnd isPathSeparator fp
-    -- an adjustant variant of 'dropTrailingPathSeparator' that normalises trailing path separators
-    -- on windows
-    dropTrailingPathSeparator' x =
-        if hasTrailingPathSeparator x
-        then let x' = dropWhileEnd isPathSeparator x
-             in if | null x' -> singleton (last x)
-                   | isDrive x -> addTrailingPathSeparator x'
-                   | otherwise -> x'
-        else x
+    dropExcessTrailingPathSeparators x
+      | hasTrailingPathSeparator x
+      , let x' = dropWhileEnd isPathSeparator x
+      , otherwise = if | null x' -> singleton (last x)
+                       | otherwise -> addTrailingPathSeparator x'
+      | otherwise = x
 
     -- an "incomplete" UNC is one without a path (but potentially a drive)
     isIncompleteUNC (pref, suff) = null suff && not (hasPenultimateColon pref)
@@ -684,7 +681,7 @@ splitFileName_ fp
     -- e.g. @//?/a:/@ or @//?/a://@, but not @//?/a:@
     hasPenultimateColon pref
       | hasTrailingPathSeparator pref
-      = maybe False (maybe False ((== _colon) . snd) . unsnoc . fst) . unsnoc . dropTrailingPathSeparator' $ pref
+      = maybe False (maybe False ((== _colon) . snd) . unsnoc . fst) . unsnoc . dropExcessTrailingPathSeparators $ pref
       | otherwise = False
 
 -- | Set the filename.