#include<coroutine>struct resumable {   struct promise_type;   using coro_handle = std::coroutine_handle<promise_type>;   resumable(coro_handle handle) : handle_(handle) {}   resumable(resumable&) = delete;   ~resumable() { if (handle_) { handle_.destroy(); } }   coro_handle handle_;};struct Allocator;struct resumable::promise_type {   void* operator new(std::size_t sz, Allocator&);   std::coroutine_handle<promise_type> get_return_object() { return std::coroutine_handle<promise_type>::from_promise(*this); }   auto initial_suspend() { return std::suspend_always(); }   auto final_suspend() noexcept { return std::suspend_always(); }   void unhandled_exception() {}   void return_void() {};};resumable foo() {    co_return;}

<source>:26:11: error: 'operator new' is provided by 'std::__n4861::__coroutine_traits_impl<resumable, void>::promise_type' {aka 'resumable::promise_type'} but is not usable with the function signature 'resumable foo()'   26 | resumable foo() {      |           ^~~