fixed out of scope error for eager self-posts of generators.

closes #142.

include/boost/cobalt/detail/generator.hpp

@@ -9,6 +9,7 @@
 #define BOOST_COBALT_DETAIL_GENERATOR_HPP
 
 #include <boost/cobalt/concepts.hpp>
+#include <boost/cobalt/error.hpp>
 #include <boost/cobalt/result.hpp>
 #include <boost/cobalt/detail/exception.hpp>
 #include <boost/cobalt/detail/forward_cancellation.hpp>
@@ -269,8 +270,16 @@ struct generator_receiver : generator_receiver_base<Yield, Push>
       if (self->yield_from != nullptr && !self->lazy)
       {
         auto exec = self->yield_from->get_executor();
+        auto alloc = asio::get_associated_allocator(self->yield_from);
         asio::post(
-            std::move(exec), std::exchange(self->yield_from, nullptr));
+            std::move(exec),
+            asio::bind_allocator(
+                alloc,
+                [y = std::exchange(self->yield_from, nullptr)]() mutable
+                {
+                  if (y->receiver) // make sure we only resume eagerly when attached to a generator object
+                    std::move(y)();
+                }));
       }
 
       return {system::in_place_value, self->get_result()};
@@ -490,8 +499,9 @@ struct generator_yield_awaitable
     return res;
   }
 
-  Push await_resume()
+  Push await_resume(const boost::source_location & loc = BOOST_CURRENT_LOCATION)
   {
+    BOOST_ASSERT(self->receiver);
     BOOST_ASSERT(self->receiver->pushed_value);
     return *std::exchange(self->receiver->pushed_value, std::nullopt);
   }

test/generator.cpp

@@ -283,4 +283,19 @@ CO_TEST_CASE(detached_)
   co_return;
 }
 
+cobalt::generator<int, int> detached_push()
+{
+  int i = co_yield 42;
+  while (true)
+    i = co_yield i;
+  co_return i;
+}
+
+CO_TEST_CASE(detached_push_)
+{
+  auto g = detached_push();
+
+  co_await g(1);
+}
+
 BOOST_AUTO_TEST_SUITE_END();