From 712dbbbedbb47f7c33cc554ce7b83f3a04e682e6 Mon Sep 17 00:00:00 2001
From: "Michael J. Sullivan" <sully@msully.net>
Date: Wed, 26 Sep 2018 15:46:26 -0700
Subject: [PATCH 1/2] Don't report "function does not return a value" in
 dynamic functions

Fixes a regression introduced in #5663.
---
 mypy/checkexpr.py                   | 6 +++++-
 test-data/unit/check-functions.test | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index ecbb356f7b4d3..0ba58694792e2 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -315,7 +315,11 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
                 self.check_protocol_issubclass(e)
         if isinstance(ret_type, UninhabitedType) and not ret_type.ambiguous:
             self.chk.binder.unreachable()
-        if not allow_none_return and self.always_returns_none(e.callee):
+        # Warn on calls to functions that always return None. The check
+        # of ret_type is both a common-case optimization and prevents reporting
+        # the error in dynamic functions (where it will be Any).
+        if (not allow_none_return and isinstance(ret_type, NoneTyp)
+                and self.always_returns_none(e.callee)):
             self.chk.msg.does_not_return_value(callee_type, e)
             return AnyType(TypeOfAny.from_error)
         return ret_type
diff --git a/test-data/unit/check-functions.test b/test-data/unit/check-functions.test
index 890d0be2dc188..15d7a50d2490e 100644
--- a/test-data/unit/check-functions.test
+++ b/test-data/unit/check-functions.test
@@ -2376,3 +2376,11 @@ def Y(x: Optional[str] = X(x_in)): ...
 
 xx: Optional[int] = X(x_in)
 [out]
+
+[case testNoComplainNoneReturnFromUntyped]
+def foo() -> None:
+    pass
+
+def lol():
+    1+'uh'
+    x = foo()

From f5ffd97e23e30f28363ffc759736a7065b5aa2ba Mon Sep 17 00:00:00 2001
From: "Michael J. Sullivan" <sully@msully.net>
Date: Wed, 26 Sep 2018 16:18:37 -0700
Subject: [PATCH 2/2] quick cleanup

---
 test-data/unit/check-functions.test | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test-data/unit/check-functions.test b/test-data/unit/check-functions.test
index 15d7a50d2490e..876a5fe43f0ce 100644
--- a/test-data/unit/check-functions.test
+++ b/test-data/unit/check-functions.test
@@ -2382,5 +2382,4 @@ def foo() -> None:
     pass
 
 def lol():
-    1+'uh'
     x = foo()