Coroutine support (C++20)

The coroutine support library defines several types that provide compile and run-time support for coroutines.

Coroutine traits

Defined in header <coroutine>
coroutine_traits (C++20)	trait type for discovering coroutine promise types (class template)

Coroutine handle

Defined in header <coroutine>
coroutine_handle (C++20)	used to refer to a suspended or executing coroutine (class template)

No-op coroutines

Defined in header <coroutine>
noop_coroutine (C++20)	creates a coroutine handle that has no observable effects when resumed or destroyed (function)
noop_coroutine_promise (C++20)	used for coroutines with no observable effects (class)
noop_coroutine_handle (C++20)	std::coroutine_handle<std::noop_coroutine_promise>, intended to refer to a no-op coroutine (typedef)

Trivial awaitables

Defined in header <coroutine>
suspend_never (C++20)	indicates that an await-expression should never suspend (class)
suspend_always (C++20)	indicates that an await-expression should always suspend (class)