这个Ada程序中的错误是什么？

Question

此Ada2012程序中的错误是什么？

with Ada.Iterator_Interfaces;

package My is

   type Cursor is private;

   function Has_Element (Position: Cursor) return Boolean;

   package Base_Iterators is new Ada.Iterator_Interfaces(Cursor, Has_Element);

   type Bindings_Iterator is new Base_Iterators.Forward_Iterator with private;

   overriding function First (Object: Bindings_Iterator) return Cursor;

   overriding function Next (Object: Bindings_Iterator; Position: Cursor) return Cursor;

private

   type Iterated_Object is access all Integer;

   type Cursor is new Iterated_Object;

   type Bindings_Iterator is new Base_Iterators.Forward_Iterator with null record;

end My;

尝试检查语法和语义：

$ gnatgcc -gnat2012 -c my.ads 
my.ads:23:09: type must be declared abstract or "First" overridden
my.ads:23:09: "First" has been inherited from subprogram at a-iteint.ads:26, instance at line 9

据我所知，First是被我覆盖的。我不明白编译器在抱怨什么。

Answer 1

该错误源于Cursor是私有派生的访问类型。将其更改为

type Cursor is access all Integer;

移除错误，将其更改为记录类型或数字类型也是如此。将Iterated_Object和Cursor的完整定义移动到公共视图也可以消除错误。

我想你偶然发现了一个编译器错误。