Fix error message in replace-match for subexpressions

* src/search.c (Freplace_match): Output a more understandable
error message when replacing a subexpression (bug#19208).

1 files changed, 6 insertions, 0 deletions

diff --git a/src/search.c b/src/search.c
index 2fa8b277195..0e2ae059e81 100644
--- a/src/search.c
+++ b/src/search.c
@@ -2404,6 +2404,12 @@ since only regular expressions have distinguished subexpressions.  */)
         args_out_of_range (subexp, make_fixnum (search_regs.num_regs));
     }
 
+  /* Check whether the subexpression to replace is greater than the
+     number of subexpressions in the regexp. */
+  if (sub > 0 && search_regs.start[sub] == -1)
+    args_out_of_range (build_string ("Attempt to replace regexp subexpression that doesn't exist"),
+                       subexp);
+
   /* Sanity check to see whether the text to replace is present in the
      buffer/string. */
   if (NILP (string))