commit 22f17a29cd0b0cc3107dc6cd1d96c62eee52a7d9
author Bram Moolenaar <Bram@vim.org> Mon Jun 21 20:48:58 2021 +0200
committer Bram Moolenaar <Bram@vim.org> Mon Jun 21 20:48:58 2021 +0200
tree b4f07018a9d2d00cea788c9f39dade141d9c3010
parent cb54bc65625abad9a0af501acac5c70fba17e2cc

patch 8.2.3031: no error if a function name starts with an underscore

Problem:    No error if a function name starts with an underscore. (Naohiro
            Ono)
Solution:   In Vim9 script disallow a function name starting with an
            underscore, as is mentioned in the help. (closes #8414)

src/userfunc.c

diff --git a/src/userfunc.c b/src/userfunc.c
index 56b7df3..e2e745c 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -3595,7 +3595,8 @@
 		lead += (int)STRLEN(sid_buf);
 	}
     }
-    else if (!(flags & TFN_INT) && builtin_function(lv.ll_name, len))
+    else if (!(flags & TFN_INT) && (builtin_function(lv.ll_name, len)
+				   || (in_vim9script() && *lv.ll_name == '_')))
     {
 	semsg(_("E128: Function name must start with a capital or \"s:\": %s"),
 								       start);