patch 8.2.0291: Vim9: assigning [] to list<string> doesn't work

Problem:    Vim9: assigning [] to list<string> doesn't work.
Solution:   Use void for empty list and dict. (Ken Takata, closes #5669)

src/globals.h

@@ -400,6 +400,8 @@ EXTERN type_T t_partial_any INIT4(VAR_PARTIAL, -1, &t_any, NULL);
 
 EXTERN type_T t_list_any INIT4(VAR_LIST, 0, &t_any, NULL);
 EXTERN type_T t_dict_any INIT4(VAR_DICT, 0, &t_any, NULL);
+EXTERN type_T t_list_empty INIT4(VAR_LIST, 0, &t_void, NULL);
+EXTERN type_T t_dict_empty INIT4(VAR_DICT, 0, &t_void, NULL);
 
 EXTERN type_T t_list_number INIT4(VAR_LIST, 0, &t_number, NULL);
 EXTERN type_T t_list_string INIT4(VAR_LIST, 0, &t_string, NULL);
@@ -1496,7 +1498,7 @@ EXTERN int netbeansSuppressNoLines INIT(= 0); // skip "No lines in buffer"
  * Excluded are errors that are only used once and debugging messages.
  */
 EXTERN char e_abort[]		INIT(= N_("E470: Command aborted"));
-EXTERN char e_argreq[]	INIT(= N_("E471: Argument required"));
+EXTERN char e_argreq[]		INIT(= N_("E471: Argument required"));
 EXTERN char e_backslash[]	INIT(= N_("E10: \\ should be followed by /, ? or &"));
 #ifdef FEAT_CMDWIN
 EXTERN char e_cmdwin[]	INIT(= N_("E11: Invalid in command-line window; <CR> executes, CTRL-C quits"));
@@ -1639,7 +1641,7 @@ EXTERN char e_invalblob[]	INIT(= N_("E978: Invalid operation for Blob"));
 EXTERN char e_toomanyarg[]	INIT(= N_("E118: Too many arguments for function: %s"));
 EXTERN char e_toofewarg[]	INIT(= N_("E119: Not enough arguments for function: %s"));
 EXTERN char e_func_deleted[]	INIT(= N_("E933: Function was deleted: %s"));
-EXTERN char e_dictkey[]	INIT(= N_("E716: Key not present in Dictionary: %s"));
+EXTERN char e_dictkey[]		INIT(= N_("E716: Key not present in Dictionary: %s"));
 EXTERN char e_listreq[]		INIT(= N_("E714: List required"));
 EXTERN char e_listblobreq[]	INIT(= N_("E897: List or Blob required"));
 EXTERN char e_listdictarg[]	INIT(= N_("E712: Argument of %s must be a List or Dictionary"));

src/testdir/test_vim9_script.vim

@@ -40,9 +40,8 @@ def Test_assignment()
   let list1: list<string> = ['sdf', 'asdf']
   let list2: list<number> = [1, 2, 3]
 
-  " TODO: does not work yet
+  let listS: list<string> = []
-  " let listS: list<string> = []
+  let listN: list<number> = []
-  " let listN: list<number> = []
 
   let dict1: dict<string> = #{key: 'value'}
   let dict2: dict<number> = #{one: 1, two: 2}

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    291,
 /**/
     290,
 /**/

src/vim9compile.c

@@ -211,6 +211,8 @@ get_list_type(type_T *member_type, garray_T *type_list)
     // recognize commonly used types
     if (member_type->tt_type == VAR_UNKNOWN)
 	return &t_list_any;
+    if (member_type->tt_type == VAR_VOID)
+	return &t_list_empty;
     if (member_type->tt_type == VAR_NUMBER)
 	return &t_list_number;
     if (member_type->tt_type == VAR_STRING)
@@ -234,6 +236,8 @@ get_dict_type(type_T *member_type, garray_T *type_list)
     // recognize commonly used types
     if (member_type->tt_type == VAR_UNKNOWN)
 	return &t_dict_any;
+    if (member_type->tt_type == VAR_VOID)
+	return &t_dict_empty;
     if (member_type->tt_type == VAR_NUMBER)
 	return &t_dict_number;
     if (member_type->tt_type == VAR_STRING)
@@ -813,11 +817,12 @@ generate_NEWLIST(cctx_T *cctx, int count)
     // drop the value types
     stack->ga_len -= count;
 
-    // use the first value type for the list member type
+    // Use the first value type for the list member type.  Use "void" for an
+    // empty list.
     if (count > 0)
 	member = ((type_T **)stack->ga_data)[stack->ga_len];
     else
-	member = &t_any;
+	member = &t_void;
     type = get_list_type(member, type_list);
 
     // add the list type to the type stack
@@ -848,11 +853,12 @@ generate_NEWDICT(cctx_T *cctx, int count)
     // drop the key and value types
     stack->ga_len -= 2 * count;
 
-    // use the first value type for the list member type
+    // Use the first value type for the list member type.  Use "void" for an
+    // empty dict.
     if (count > 0)
 	member = ((type_T **)stack->ga_data)[stack->ga_len + 1];
     else
-	member = &t_any;
+	member = &t_void;
     type = get_dict_type(member, type_list);
 
     // add the dict type to the type stack
@@ -1854,8 +1860,13 @@ check_type(type_T *expected, type_T *actual, int give_msg)
 	}
 	if (expected->tt_type == VAR_DICT || expected->tt_type == VAR_LIST)
 	{
-	    int ret = check_type(expected->tt_member, actual->tt_member,
+	    int ret;
-									FALSE);
+
+	    // void is used for an empty list or dict
+	    if (actual->tt_member == &t_void)
+		ret = OK;
+	    else
+		ret = check_type(expected->tt_member, actual->tt_member, FALSE);
 	    if (ret == FAIL && give_msg)
 		type_mismatch(expected, actual);
 	    return ret;
@@ -1873,7 +1884,7 @@ check_type(type_T *expected, type_T *actual, int give_msg)
     static int
 need_type(type_T *actual, type_T *expected, int offset, cctx_T *cctx)
 {
-    if (equal_type(actual, expected) || expected->tt_type == VAR_UNKNOWN)
+    if (check_type(expected, actual, FALSE))
 	return OK;
     if (actual->tt_type != VAR_UNKNOWN)
     {