Fixed memory corruption when using a node as a key

include/yaml-cpp/node/impl.h

@@ -380,6 +380,7 @@ inline const Node Node::operator[](const Node& key) const {
     throw InvalidNode();
   EnsureNodeExists();
   key.EnsureNodeExists();
+  m_pMemory->merge(*key.m_pMemory);
   detail::node& value =
       static_cast<const detail::node&>(*m_pNode).get(*key.m_pNode, m_pMemory);
   return Node(value, m_pMemory);
@@ -390,6 +391,7 @@ inline Node Node::operator[](const Node& key) {
     throw InvalidNode();
   EnsureNodeExists();
   key.EnsureNodeExists();
+  m_pMemory->merge(*key.m_pMemory);
   detail::node& value = m_pNode->get(*key.m_pNode, m_pMemory);
   return Node(value, m_pMemory);
 }

test/node/node_test.cpp

@@ -258,5 +258,16 @@ TEST(NodeTest, CloneNull) {
   Node clone = Clone(node);
   EXPECT_EQ(NodeType::Null, clone.Type());
 }
+
+TEST(NodeTest, KeyNodeExitsScope) {
+  Node node;
+  {
+    Node temp("Hello, world");
+    node[temp] = 0;
+  }
+  for (const auto &kv : node) {
+    (void)kv;
+  }
+}
 }
 }