cannot use item->const_item() in open_table_from_share()

because table->map is set much later.
Use check_vcol_func_processor() to detect fields too.

sql/item.h

@@ -2511,6 +2511,10 @@ public:
   bool enumerate_field_refs_processor(void *arg);
   bool update_table_bitmaps_processor(void *arg);
   bool switch_to_nullable_fields_processor(void *arg);
+  bool check_vcol_func_processor(void *arg)
+  { // may be, a special flag VCOL_FIELD ?
+    return mark_unsupported_function(field_name, arg, VCOL_UNKNOWN);
+  }
   void cleanup();
   Item_equal *get_item_equal() { return item_equal; }
   void set_item_equal(Item_equal *item_eq) { item_equal= item_eq; }

sql/table.cc

@@ -3041,8 +3041,8 @@ enum open_frm_error open_table_from_share(THD *thd, TABLE_SHARE *share,
           goto err;
         }
         field->default_value= vcol;
-        if (is_create_table && vcol->expr_item->const_item() &&
-            !(vcol->flags & (VCOL_NON_DETERMINISTIC | VCOL_TIME_FUNC)))
+        if (is_create_table &&
+            !(vcol->flags & (VCOL_UNKNOWN | VCOL_NON_DETERMINISTIC | VCOL_TIME_FUNC)))
         {
           enum_check_fields old_count_cuted_fields= thd->count_cuted_fields;
           thd->count_cuted_fields= CHECK_FIELD_WARN;    // To find wrong default values