1 files changed, 11 insertions, 1 deletions
diff --git a/runtime/lua/vim/shared.lua b/runtime/lua/vim/shared.lua
index 36df24d0c1..6eb7a970e4 100644
--- a/runtime/lua/vim/shared.lua
+++ b/runtime/lua/vim/shared.lua
@@ -21,7 +21,7 @@ vim.deepcopy = (function()
     table = function(orig)
       local copy = {}
 
-      if getmetatable(orig) == vim._empty_dict_mt then
+      if vim._empty_dict_mt ~= nil and getmetatable(orig) == vim._empty_dict_mt then
         copy = vim.empty_dict()
       end
 
@@ -174,9 +174,19 @@ function vim.tbl_extend(behavior, ...)
   if (behavior ~= 'error' and behavior ~= 'keep' and behavior ~= 'force') then
     error('invalid "behavior": '..tostring(behavior))
   end
+
+  if select('#', ...) < 2 then
+    error('wrong number of arguments (given '..tostring(1 + select('#', ...))..', expected at least 3)')
+  end
+
   local ret = {}
+  if vim._empty_dict_mt ~= nil and getmetatable(select(1, ...)) == vim._empty_dict_mt then
+    ret = vim.empty_dict()
+  end
+
   for i = 1, select('#', ...) do
     local tbl = select(i, ...)
+    vim.validate{["after the second argument"] = {tbl,'t'}}
     if tbl then
       for k, v in pairs(tbl) do
         if behavior ~= 'force' and ret[k] ~= nil then