neater

sugar/file.rkt

@@ -8,10 +8,12 @@
 ;; this is identical to `filename-extension` in `racket/path`
 ;; but will not treat hidden files as an extension (which is a bug)
 (define (filename-extension name)
-  (define filename (file-name-from-path name))
-  (define bytes (and filename (path->bytes filename)))
-  (match (and bytes (regexp-match #rx#".[.]([^.]+)$" bytes))
+  (match (file-name-from-path name)
+    [(? path-for-some-system? filename)
+     (=> resume)
+     (match (regexp-match #rx#".[.]([^.]+)$" (path->bytes filename))
        [(list _ second) second]
+       [_ (resume)])]
     [_ #false]))
 
 (module+ test