vim-patch:8.2.2920: still a way to shadow a builtin function

Problem:    Still a way to shadow a builtin function. (Yasuhiro Matsumoto)
Solution:   Check the key when using extend(). (issue vim/vim#8302)

https://github.com/vim/vim/commit/6f1d2aa437744a7cb0206fdaa543a788c5a56c79

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

3 files changed, 24 insertions, 5 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 5b5b4d259c..72df343932 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -1760,11 +1760,7 @@ void set_var_lval(lval_T *lp, char *endp, typval_T *rettv, int copy, const bool
         semsg(_(e_dictkey), lp->ll_newkey);
         return;
       }
-      if ((lp->ll_tv->vval.v_dict == &globvardict
-           // || lp->ll_tv->vval.v_dict == &SCRIPT_ITEM(current_sctx.sc_sid)->sn_vars->sv_dict
-           )
-          && (rettv->v_type == VAR_FUNC || rettv->v_type == VAR_PARTIAL)
-          && var_wrong_func_name(lp->ll_newkey, true)) {
+      if (tv_dict_wrong_func_name(lp->ll_tv->vval.v_dict, rettv, lp->ll_newkey)) {
         return;
       }
 
diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index 31b73f8d48..2b44dacca4 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -2206,6 +2206,18 @@ bool tv_dict_get_callback(dict_T *const d, const char *const key, const ptrdiff_
   return res;
 }
 
+/// Check for adding a function to g: or s:.
+/// If the name is wrong give an error message and return true.
+int tv_dict_wrong_func_name(dict_T *d, typval_T *tv, const char *name)
+{
+  return (d == &globvardict
+          // || (SCRIPT_ID_VALID(current_sctx.sc_sid)
+          //     && d == &SCRIPT_ITEM(current_sctx.sc_sid)->sn_vars->sv_dict)
+          )
+         && (tv->v_type == VAR_FUNC || tv->v_type == VAR_PARTIAL)
+         && var_wrong_func_name(name, true);
+}
+
 //{{{2 dict_add*
 
 /// Add item to dictionary
@@ -2217,6 +2229,9 @@ bool tv_dict_get_callback(dict_T *const d, const char *const key, const ptrdiff_
 int tv_dict_add(dict_T *const d, dictitem_T *const item)
   FUNC_ATTR_NONNULL_ALL
 {
+  if (tv_dict_wrong_func_name(d, &item->di_tv, (const char *)item->di_key)) {
+    return FAIL;
+  }
   return hash_add(&d->dv_hashtab, item->di_key);
 }
 
@@ -2477,6 +2492,9 @@ void tv_dict_extend(dict_T *const d1, dict_T *const d2, const char *const action
           || var_check_ro(di1->di_flags, arg_errmsg, arg_errmsg_len)) {
         break;
       }
+      if (tv_dict_wrong_func_name(d1, &di2->di_tv, (const char *)di2->di_key)) {
+        break;
+      }
 
       if (watched) {
         tv_copy(&di1->di_tv, &oldtv);
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index afeea20f2d..011e9e000e 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -2488,6 +2488,11 @@ func Test_builtin_check()
   call assert_fails('let g:.trim = {x -> " " .. x}', 'E704:')
   call assert_fails('let s:["trim"] = {x -> " " .. x}', 'E704:')
   call assert_fails('let s:.trim = {x -> " " .. x}', 'E704:')
+
+  call assert_fails('call extend(g:, #{foo: { -> "foo" }})', 'E704:')
+  let g:bar = 123
+  call extend(g:, #{bar: { -> "foo" }}, "keep")
+  call assert_fails('call extend(g:, #{bar: { -> "foo" }}, "force")', 'E704:')
 endfunc