public subscript() -> T { @_transparent unsafeAddress { UnsafePointer<T>(pointer) } @_transparent nonmutating unsafeMutableAddress { pointer } } public subscript() -> T { @_transparent unsafeAddress { UnsafePointer<T>(pointer) } @_transparent nonmutating unsafeMutableAddress { pointer } }let intOnHeap = Box<Int>(0) XCTAssertEqual(intOnHeap[], 0) なるほどそのまま引数のないsubscriptになるのか