Add basic yield from type inference. References #647.

test/completion/generators.py

@@ -175,3 +175,25 @@ gen().send()
 
 #? 
 gen()()
+
+# -----------------
+# yield from
+# -----------------
+
+# python >= 3.3
+
+def yield_from():
+    yield from iter([1])
+
+#? int()
+next(yield_from())
+
+def yield_from_multiple():
+    yield from iter([1])
+    yield str()
+
+x, y = yield_from_multiple()
+#? int()
+x
+#? str()
+y

test/completion/pep0484_comments.py

@@ -49,7 +49,7 @@ class Employee:
 
 # The typing library is not installable for Python 2.6, therefore ignore the
 # following tests.
-# python > 2.6
+# python >= 2.7
 
 from typing import List
 x = []   # type: List[Employee]