vim-patch:8.2.0469: Vim9: no error for missing ] after list

Problem:    Vim9: no error for missing ] after list.
Solution:   Add error message. Add more tests.

ee619e5bc0

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

src/nvim/eval/userfunc.c

@@ -297,6 +297,7 @@ int get_lambda_tv(char **arg, typval_T *rettv, bool evaluate)
   e = (char_u *)(*arg);
   *arg = skipwhite(*arg);
   if (**arg != '}') {
+    semsg(_("E451: Expected }: %s"), *arg);
     goto errret;
   }
   (*arg)++;