add coroutine behavior for generators

coroutines don't have __next__; they also call themselves coroutines.
This does not change the fact that `async def` methods are generators,
but it does make them behave more like CPython.

2 files changed, 14 insertions, 0 deletions

diff --git a/tests/basics/async_coroutine.py b/tests/basics/async_coroutine.py
new file mode 100644
index 000000000..791f6df14
--- /dev/null
+++ b/tests/basics/async_coroutine.py
@@ -0,0 +1,13 @@
+async def f():
+    pass
+
+try:
+    f()  # Should not crash
+except Exception as e:
+    print('failed to invoke')
+
+try:
+    next(f())
+    print('This should fail because async def returns a coroutine, and next() is not allowed')
+except Exception as e:
+    print('pass')
diff --git a/tests/basics/async_coroutine.py.exp b/tests/basics/async_coroutine.py.exp
new file mode 100644
index 000000000..2ae28399f
--- /dev/null
+++ b/tests/basics/async_coroutine.py.exp
@@ -0,0 +1 @@
+pass