From cb2dc2c8e4fefcc3dd38ed90e2aca02bc1e82e2c Mon Sep 17 00:00:00 2001
From: Zejun Wu <watashi@fb.com>
Date: Thu, 17 Jul 2014 09:49:39 -0700
Subject: [PATCH] Check for self-assignment in move assignment

Summary:
Check for self-assignment in move assignment. Otherwise
Optional<Neko> cat = whatever;
cat = std::move(cat);
cat.hasValue(); // always returns false

Test Plan: fbmake runtests

Reviewed By: tjackson@fb.com

FB internal diff: D1440633
---
 folly/Optional.h            | 12 +++++++-----
 folly/test/OptionalTest.cpp | 10 ++++++++++
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/folly/Optional.h b/folly/Optional.h
index 701d744e..eb8de160 100644
--- a/folly/Optional.h
+++ b/folly/Optional.h
@@ -136,11 +136,13 @@ class Optional {
   }
 
   void assign(Optional&& src) {
-    if (src.hasValue()) {
-      assign(std::move(src.value()));
-      src.clear();
-    } else {
-      clear();
+    if (this != &src) {
+      if (src.hasValue()) {
+        assign(std::move(src.value()));
+        src.clear();
+      } else {
+        clear();
+      }
     }
   }
 
diff --git a/folly/test/OptionalTest.cpp b/folly/test/OptionalTest.cpp
index ff82abdc..79968d01 100644
--- a/folly/test/OptionalTest.cpp
+++ b/folly/test/OptionalTest.cpp
@@ -379,6 +379,16 @@ TEST(Optional, MakeOptional) {
   EXPECT_EQ(**optIntPtr, 3);
 }
 
+TEST(Optional, SelfAssignment) {
+  Optional<int> a = 42;
+  a = a;
+  ASSERT_TRUE(a.hasValue() && a.value() == 42);
+
+  Optional<int> b = 23333333;
+  b = std::move(b);
+  ASSERT_TRUE(b.hasValue() && b.value() == 23333333);
+}
+
 class ContainsOptional {
  public:
   ContainsOptional() { }
-- 
2.34.1