patch 8.2.2323: Vim9: error when inferring type from empty dict/list

Problem:    Vim9: error when inferring type from empty dict/list.
Solution:   When the member is t_unknown use t_any. (closes #7009)

Author: brammool

src/testdir/test_vim9_expr.vim

@@ -2929,6 +2929,16 @@ def Test_expr7_list_subscript()
   lines = ['var l = [0, 1, 2]', 'echo l[g:astring : g:theone]']
   CheckDefExecFailure(lines, 'E1012:')
   CheckScriptFailure(['vim9script'] + lines, 'E1030:', 3)
+
+  lines =<< trim END
+      vim9script
+      var ld = []
+      def Func()
+        eval ld[0].key
+      enddef
+      defcompile
+  END
+  CheckScriptSuccess(lines)
 enddef
 
 def Test_expr7_dict_subscript()
@@ -2937,6 +2947,15 @@ def Test_expr7_dict_subscript()
       var l = [{lnum: 2}, {lnum: 1}]
       var res = l[0].lnum > l[1].lnum
       assert_true(res)
+
+      var dd = {}
+      def Func1()
+        eval dd.key1.key2
+      enddef
+      def Func2()
+        eval dd['key1'].key2
+      enddef
+      defcompile
   END
   CheckScriptSuccess(lines)
 enddef

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2323,
 /**/
     2322,
 /**/

src/vim9compile.c

@@ -1899,7 +1899,10 @@ generate_STRINGMEMBER(cctx_T *cctx, char_u *name, size_t len)
     }
     // change dict type to dict member type
     if (type->tt_type == VAR_DICT)
-	((type_T **)stack->ga_data)[stack->ga_len - 1] = type->tt_member;
+    {
+	((type_T **)stack->ga_data)[stack->ga_len - 1] =
+		      type->tt_member == &t_unknown ? &t_any : type->tt_member;
+    }
 
     return OK;
 }
@@ -3793,7 +3796,12 @@ compile_subscript(
 		    return FAIL;
 		}
 		if ((*typep)->tt_type == VAR_DICT)
+		{
 		    *typep = (*typep)->tt_member;
+		    if (*typep == &t_unknown)
+			// empty dict was used
+			*typep = &t_any;
+		}
 		else
 		{
 		    if (need_type(*typep, &t_dict_any, -2, cctx,
@@ -3831,7 +3839,12 @@ compile_subscript(
 		else
 		{
 		    if ((*typep)->tt_type == VAR_LIST)
+		    {
 			*typep = (*typep)->tt_member;
+			if (*typep == &t_unknown)
+			    // empty list was used
+			    *typep = &t_any;
+		    }
 		    if (generate_instr_drop(cctx,
 			     vtype == VAR_LIST ?  ISN_LISTINDEX : ISN_ANYINDEX,
 								    1) == FAIL)