Currently, if a coroutine function is declared noexcept, this triggers std::terminate on alloc fail.

I would like to suggest that if frame construction fails due to memory, the compiler attempts to construct a value of Ret using an instance of std::bad_alloc{} before throwing std::bad_alloc (and calling std::terminate if marked noexcept)

For example:

class coroutine_type

{

   struct promise_type { ... } 

private:

   coroutine_type (promise_type *) { ... }
public:

   coroutine_type(std::bad_alloc) { 

      // Handle here

   }

};

This would allow declaring noexcept coroutine functions like:

coroutine_type myfunc(...) noexcept;