WIP Revert to Lazy coroutines

rt/promise.hpp

-#ifndef __PROMISE_HPP__
-#define __PROMISE_HPP__
-
-
-#include <type_traits>
-
-#include <result.hpp>
-
-
-namespace typon
-{
-
-  template <typename T>
-  struct promise
-  {
-    result<T>* _result;
-
-    template <typename U>
-    void return_value(U&& expr) noexcept(std::is_nothrow_constructible_v<T, U&&>)
-    {
-      _result->return_value(std::forward<U>(expr));
-    }
-
-    void unhandled_exception() noexcept
-    {
-      _result->unhandled_exception();
-    }
-  };
-
-
-  template <>
-  struct promise<void>
-  {
-    result<void>* _result;
-
-    void return_void() noexcept {}
-
-    void unhandled_exception() noexcept
-    {
-      _result->unhandled_exception();
-    }
-  };
-
-}
-
-#endif // __PROMISE_HPP__

rt/result.hpp

@@ -18,7 +18,6 @@ namespace typon
     {
       T _value;
     };
-    bool _ready;
 
     ~result()
     {
@@ -32,18 +31,11 @@ namespace typon
     void return_value(U&& expr) noexcept(std::is_nothrow_constructible_v<T, U&&>)
     {
       std::construct_at(std::addressof(_value), std::forward<U>(expr));
-      _ready = true;
     }
 
     void unhandled_exception() noexcept
     {
       _exception = std::current_exception();
-      _ready = true;
-    }
-
-    bool ready() const noexcept
-    {
-      return _ready;
     }
 
     T& get() &
@@ -71,18 +63,15 @@ namespace typon
   {
     T* _value;
     std::exception_ptr _exception;
-    bool _ready;
 
     void return_value(T& expr) noexcept
     {
       _value = std::addressof(expr);
-      _ready = true;
     }
 
     void unhandled_exception() noexcept
     {
       _exception = std::current_exception();
-      _ready = true;
     }
 
     T& get() &
@@ -100,17 +89,12 @@ namespace typon
   struct result<void>
   {
     std::exception_ptr _exception;
-    bool _ready;
 
-    void return_void() noexcept
-    {
-      _ready = true;
-    }
+    void return_void() noexcept {}
 
     void unhandled_exception() noexcept
     {
       _exception = std::current_exception();
-      _ready = true;
     }
 
     void get()

rt/task.hpp

@@ -4,7 +4,6 @@
 #include <coroutine>
 
 #include <result.hpp>
-#include <promise.hpp>
 
 
 namespace typon
@@ -16,64 +15,48 @@ namespace typon
     struct promise_type;
 
     std::coroutine_handle<promise_type> _coroutine;
-    result<T> _result;
 
-    struct promise_type : promise<T>
+    ~task()
+    {
+      _coroutine.destroy();
+    }
+
+    struct promise_type : result<T>
     {
       std::coroutine_handle<> _continuation;
 
       task get_return_object() noexcept
       {
-        task t {};
-        auto h = std::coroutine_handle<promise_type>::from_promise(*this);
-        t._coroutine = h;
-        h.promise()._result = std::addressof(t._result);
-        return t;
+        return { std::coroutine_handle<promise_type>::from_promise(*this) };
       }
 
-      std::suspend_never initial_suspend() noexcept
+      std::suspend_always initial_suspend() noexcept
       {
         return {};
       }
 
       auto final_suspend() noexcept
       {
-        struct awaitable
+        struct awaitable : std::suspend_always
         {
-          bool _ready;
-
-          bool await_ready() noexcept
-          {
-            return _ready;
-          }
-
           std::coroutine_handle<> await_suspend(std::coroutine_handle<promise_type> coroutine) noexcept
           {
             return coroutine.promise()._continuation;
           }
-
-          void await_resume() noexcept {}
         };
 
-        return awaitable { !_continuation };
+        return awaitable {};
       }
     };
 
-    auto operator co_await() && noexcept
+    auto operator co_await() const&& noexcept
     {
       struct awaitable
       {
         std::coroutine_handle<promise_type> _coroutine;
-        result<T> * _result;
-        bool _destroy;
 
         bool await_ready() noexcept
         {
-          if (_result->ready())
-          {
-            return true;
-          }
-          _destroy = true;
           return false;
         }
 
@@ -85,20 +68,18 @@ namespace typon
 
         decltype(auto) await_resume()
         {
-          if (_destroy)
-          {
-            _coroutine.destroy();
-          }
-          return _result->get();
+          return _coroutine.promise().get();
         }
       };
 
-      return awaitable { _coroutine, std::addressof(_result), false };
+      return awaitable { _coroutine };
     }
 
-    decltype(auto) call() &&
+    decltype(auto) call() const&&
     {
-      return _result.get();
+      _coroutine.promise()._continuation = std::noop_coroutine();
+      _coroutine.resume();
+      return _coroutine.promise().get();
     }
   };