Cleaning up base::Value assignment.

base/values.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/values.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 155 matching lines @@
 
 Value::Value(const std::vector<char>& in_blob) : type_(Type::BINARY) {
   binary_value_.Init(in_blob);
 }
 
 Value::Value(std::vector<char>&& in_blob) : type_(Type::BINARY) {
   binary_value_.Init(std::move(in_blob));
 }
 
 Value& Value::operator=(const Value& that) {
-  if (this != &that) {
-    if (type_ == that.type_) {
-      InternalCopyAssignFromSameType(that);
-    } else {
-      InternalCleanup();
-      InternalCopyConstructFrom(that);
-    }
+  if (type_ == that.type_) {
+    InternalCopyAssignFromSameType(that);
+  } else {
+    // this is not a self assignment because the type_ doesn't match.
+    InternalCleanup();
+    InternalCopyConstructFrom(that);
   }
 
   return *this;
 }
 
 Value& Value::operator=(Value&& that) {
-  if (this != &that) {
-    if (type_ == that.type_) {
-      InternalMoveAssignFromSameType(std::move(that));
-    } else {
-      InternalCleanup();
-      InternalMoveConstructFrom(std::move(that));
-    }
+  if (type_ == that.type_) {
+    DCHECK(this != &that) << " attempt to self move assign.";
+    InternalMoveAssignFromSameType(std::move(that));

[dcheng, 2017/03/10 18:40:15]

We should just remove the branch entirely if we're DCHECKing.

[dyaroshev, 2017/03/10 18:54:57]

Done.
std::variant (http://en.cppreference.com/w/cpp/utility/variant/operator%3D) (on
which this is based) would check for matching types - but I've double checked -
there does not seem to be a gain.

+  } else {
+    InternalCleanup();
+    InternalMoveConstructFrom(std::move(that));
   }
 
   return *this;
 }
 
 Value::~Value() {
   InternalCleanup();
 }
 
 // static
@@ skipping 1149 matching lines @@
 }
 
 std::ostream& operator<<(std::ostream& out, const Value::Type& type) {
   if (static_cast<int>(type) < 0 ||
       static_cast<size_t>(type) >= arraysize(kTypeNames))
     return out << "Invalid Type (index = " << static_cast<int>(type) << ")";
   return out << Value::GetTypeName(type);
 }
 
 }  // namespace base