cleanup: move Virtual_column_info::print out of Virtual_column_info

sql/field.h

@@ -681,7 +681,7 @@ class Virtual_column_info: public Sql_alloc
     in_partitioning_expr= TRUE;
   }
   inline bool is_equal(const Virtual_column_info* vcol) const;
-  void print(String*);
+  inline void print(String*);
 };
 
 class Field: public Value_source

sql/item.cc

@@ -10715,14 +10715,3 @@ void Item::register_in(THD *thd)
   next= thd->free_list;
   thd->free_list= this;
 }
-
-void Virtual_column_info::print(String *str)
-{
-  expr->print_parenthesised(str,
-                   (enum_query_type)(QT_ITEM_ORIGINAL_FUNC_NULLIF |
-                                     QT_ITEM_IDENT_SKIP_DB_NAMES |
-                                     QT_ITEM_IDENT_SKIP_TABLE_NAMES |
-                                     QT_NO_DATA_EXPANSION |
-                                     QT_TO_SYSTEM_CHARSET),
-                   LOWEST_PRECEDENCE);
-}

sql/item.h

@@ -1292,6 +1292,23 @@ class Item: public Value_source,
   virtual enum precedence precedence() const { return DEFAULT_PRECEDENCE; }
   void print_parenthesised(String *str, enum_query_type query_type,
                            enum precedence parent_prec);
+  /**
+    This helper is used to print expressions as a part of a table definition,
+    in particular for
+      - generated columns
+      - check constraints
+      - default value expressions
+  */
+  void print_for_table_def(String *str)
+  {
+    print_parenthesised(str,
+                     (enum_query_type)(QT_ITEM_ORIGINAL_FUNC_NULLIF |
+                                       QT_ITEM_IDENT_SKIP_DB_NAMES |
+                                       QT_ITEM_IDENT_SKIP_TABLE_NAMES |
+                                       QT_NO_DATA_EXPANSION |
+                                       QT_TO_SYSTEM_CHARSET),
+                     LOWEST_PRECEDENCE);
+  }
   virtual void print(String *str, enum_query_type query_type);
   void print_item_w_name(String *str, enum_query_type query_type);
   void print_value(String *str);
@@ -5977,4 +5994,9 @@ inline bool Virtual_column_info::is_equal(const Virtual_column_info* vcol) const
       && expr->eq(vcol->expr, true);
 }
 
+inline void Virtual_column_info::print(String* str)
+{
+  expr->print_for_table_def(str);
+}
+
 #endif /* SQL_ITEM_INCLUDED */