Improve error message for old-style backquotes

* src/lread.c (load_error_old_style_backquotes): Improve error message
if no file is being loaded.

* test/src/lread-tests.el (lread-tests--force-new-style-backquotes):
Adapt test.

1 files changed, 10 insertions, 2 deletions

diff --git a/src/lread.c b/src/lread.c
index d675b563916..bcf3b7f55c7 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1006,8 +1006,16 @@ load_error_handler (Lisp_Object data)
 static _Noreturn void
 load_error_old_style_backquotes (void)
 {
-  AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
-  xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
+  if (NILP (Vload_file_name))
+    {
+      AUTO_STRING (message, "Old-style backquotes detected!");
+      xsignal1 (Qerror, message);
+    }
+  else
+    {
+      AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
+      xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
+    }
 }
 
 static void