vim-patch:8.2.3782: Vim9: no error if a function shadows a script variable (#27881)

Problem:    Vim9: no error if a function shadows a script variable.
Solution:   Check the function doesn't shadow a variable. (closes vim/vim#9310)

https://github.com/vim/vim/commit/052ff291d72bc9c176f9562f021d7e8e030e74c0

Omit EVAL_VAR_NO_FUNC: Vim9 script only.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index fe10d56d49..2ada0a0e59 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -2294,17 +2294,27 @@ void ex_function(exarg_T *eap)
       arg = fudi.fd_newkey;
     }
     if (arg != NULL && (fudi.fd_di == NULL || !tv_is_func(fudi.fd_di->di_tv))) {
-      int j = ((uint8_t)(*arg) == K_SPECIAL) ? 3 : 0;
-      while (arg[j] != NUL && (j == 0 ? eval_isnamec1(arg[j]) : eval_isnamec(arg[j]))) {
-        j++;
+      char *name_base = arg;
+      if ((uint8_t)(*arg) == K_SPECIAL) {
+        name_base = vim_strchr(arg, '_');
+        if (name_base == NULL) {
+          name_base = arg + 3;
+        } else {
+          name_base++;
+        }
       }
-      if (arg[j] != NUL) {
+      int i;
+      for (i = 0; name_base[i] != NUL && (i == 0
+                                          ? eval_isnamec1(name_base[i])
+                                          : eval_isnamec(name_base[i])); i++) {}
+      if (name_base[i] != NUL) {
         emsg_funcname(e_invarg2, arg);
       }
     }
     // Disallow using the g: dict.
     if (fudi.fd_dict != NULL && fudi.fd_dict->dv_scope == VAR_DEF_SCOPE) {
       emsg(_("E862: Cannot use g: here"));
+      goto ret_free;
     }
   }