From 9b7b3830723ade186701e88c3a5d1e9506ee737b Mon Sep 17 00:00:00 2001
From: Guido van Rossum <guido@dropbox.com>
Date: Mon, 18 Apr 2016 14:27:20 -0700
Subject: [PATCH] Make ConditionalTypeBinder a context manager.

Now we can use `with binder: X` instead of `binder.push_frame(); X; binder.pop_frame()`
---
 mypy/checker.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mypy/checker.py b/mypy/checker.py
index 8f46c3890a67..c3d1ad60c18f 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1,6 +1,7 @@
 """Mypy type checker."""
 
 import itertools
+import contextlib
 
 from typing import (
     Any, Dict, Set, List, cast, Tuple, TypeVar, Union, Optional, NamedTuple
@@ -295,6 +296,12 @@ def push_loop_frame(self):
     def pop_loop_frame(self):
         self.loop_frames.pop()
 
+    def __enter__(self) -> None:
+        self.push_frame()
+
+    def __exit__(self, *args: Any) -> None:
+        self.pop_frame()
+
 
 def meet_frames(*frames: Frame) -> Frame:
     answer = Frame()