patch 8.2.4460: Vim9: wrong error for defining dict function

Problem:    Vim9: wrong error for defining dict function.
Solution:   Explicitly check for trying to define a dict function.
            (closes 9827)

src/errors.h

@@ -3010,7 +3010,8 @@ EXTERN char e_variable_arguments_type_must_be_list_str[]
 	INIT(= N_("E1180: Variable arguments type must be a list: %s"));
 EXTERN char e_cannot_use_underscore_here[]
 	INIT(= N_("E1181: Cannot use an underscore here"));
-// E1182 unused
+EXTERN char e_cannot_define_dict_func_in_vim9_script_str[]
+	INIT(= N_("E1182: Cannot define a dict function in Vim9 script: %s"));
 EXTERN char e_cannot_use_range_with_assignment_operator_str[]
 	INIT(= N_("E1183: Cannot use a range with an assignment operator: %s"));
 #endif

src/testdir/test_vim9_func.vim

@@ -106,6 +106,63 @@ def Test_wrong_function_name()
       enddef
   END
   v9.CheckScriptFailure(lines, 'E1267:')
+
+  lines =<< trim END
+      vim9script
+      var Object = {}
+      function Object.Method()
+      endfunction
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+
+  lines =<< trim END
+      vim9script
+      var Object = {}
+      def Object.Method()
+      enddef
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+
+  lines =<< trim END
+      vim9script
+      g:Object = {}
+      function g:Object.Method()
+      endfunction
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+
+  lines =<< trim END
+      let s:Object = {}
+      def Define()
+        function s:Object.Method()
+        endfunction
+      enddef
+      defcompile
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+  delfunc g:Define
+
+  lines =<< trim END
+      let s:Object = {}
+      def Define()
+        def Object.Method()
+        enddef
+      enddef
+      defcompile
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+  delfunc g:Define
+
+  lines =<< trim END
+      let g:Object = {}
+      def Define()
+        function g:Object.Method()
+        endfunction
+      enddef
+      defcompile
+  END
+  v9.CheckScriptFailure(lines, 'E1182:')
+  delfunc g:Define
 enddef
 
 def Test_autoload_name_mismatch()

src/userfunc.c

@@ -4268,10 +4268,21 @@ define_function(exarg_T *eap, char_u *name_arg, garray_T *lines_to_free)
     }
     else
     {
-	if (vim9script && p[0] == 's' && p[1] == ':')
+	if (vim9script)
 	{
-	    semsg(_(e_cannot_use_s_colon_in_vim9_script_str), p);
-	    return NULL;
+	    if (p[0] == 's' && p[1] == ':')
+	    {
+		semsg(_(e_cannot_use_s_colon_in_vim9_script_str), p);
+		return NULL;
+	    }
+	    p = to_name_end(p, TRUE);
+	    if (*skipwhite(p) == '.' && vim_strchr(p, '(') != NULL)
+	    {
+		semsg(_(e_cannot_define_dict_func_in_vim9_script_str),
+								     eap->arg);
+		return NULL;
+	    }
+	    p = eap->arg;
 	}
 
 	name = save_function_name(&p, &is_global, eap->skip,

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4460,
 /**/
     4459,
 /**/

src/vim9compile.c

@@ -831,7 +831,11 @@ compile_nested_function(exarg_T *eap, cctx_T *cctx, garray_T *lines_to_free)
     {
 	if (!ends_excmd2(name_start, name_end))
 	{
-	    semsg(_(e_invalid_command_str), eap->cmd);
+	    if (*skipwhite(name_end) == '.')
+		semsg(_(e_cannot_define_dict_func_in_vim9_script_str),
+								     eap->cmd);
+	    else
+		semsg(_(e_invalid_command_str), eap->cmd);
 	    return NULL;
 	}