lint: Report lonely parentheses.

* guix/scripts/lint.scm (%hanging-paren-rx): New variable.
  (report-lone-parentheses): New procedure.
  (%formatting-reporters): Use it.
* tests/lint.scm ("formatting: lonely parentheses"): New test.

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/lint.scm b/tests/lint.scm
index 9634fb68e7..3f149562d4 100644
--- a/tests/lint.scm
+++ b/tests/lint.scm
@@ -512,6 +512,16 @@ requests."
           (check-source pkg))))
     "not reachable: 404")))
 
+(test-assert "formatting: lonely parentheses"
+  (string-contains
+   (with-warnings
+     (check-formatting
+      (
+       dummy-package "ugly as hell!"
+      )
+      ))
+   "lonely"))
+
 (test-assert "formatting: tabulation"
   (string-contains
    (with-warnings