class Phlex::SGML

def await(task)
	case task
	when defined?(Concurrent::IVar) && Concurrent::IVar
		flush if task.pending?
		task.wait.value
	when defined?(Async::Task) && Async::Task
		flush if task.running?
		task.wait
	else
		raise ArgumentError, "Expected an asynchronous task / promise."
	end
end