Fix return type of insert_or_assign

Summary: I misread the return types on cppreference; the overloads I implemented are supposed to return `std::pair<iterator, bool>`, not `iterator`. Whoops!

Reviewed By: yfeldblum

Differential Revision: D48375389

fbshipit-source-id: daf97a6db95c420b85dd7fcdafb84b0885bf1c9d

folly/sorted_vector_types.h

@@ -1219,21 +1219,21 @@ class sorted_vector_map : detail::growth_policy_wrapper<GrowthPolicy> {
   }
 
   template <typename M>
-  iterator insert_or_assign(const key_type& k, M&& obj) {
+  std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj) {
     auto itAndInserted = try_emplace(k, std::forward<M>(obj));
     if (!itAndInserted.second) {
       itAndInserted.first->second = std::forward<M>(obj);
     }
-    return itAndInserted.first;
+    return itAndInserted;
   }
 
   template <typename M>
-  iterator insert_or_assign(key_type&& k, M&& obj) {
+  std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj) {
     auto itAndInserted = try_emplace(std::move(k), std::forward<M>(obj));
     if (!itAndInserted.second) {
       itAndInserted.first->second = std::forward<M>(obj);
     }
-    return itAndInserted.first;
+    return itAndInserted;
   }
 
   size_type erase(const key_type& key) {

folly/test/sorted_vector_test.cpp

@@ -1489,7 +1489,9 @@ TEST(SortedVectorTypes, TestInsertOrAssign) {
   {
     auto k = folly::make_optional<int>(1);
     auto v = folly::make_optional<std::string>("1");
-    const auto it = map.insert_or_assign(std::move(k), std::move(v));
+    const auto& [it, inserted] =
+        map.insert_or_assign(std::move(k), std::move(v));
+    EXPECT_TRUE(inserted);
     EXPECT_EQ(it->first, 1);
     EXPECT_EQ(it->second, "1");
     EXPECT_FALSE(k);
@@ -1499,7 +1501,9 @@ TEST(SortedVectorTypes, TestInsertOrAssign) {
   {
     auto k = folly::make_optional<int>(1);
     auto v = folly::make_optional<std::string>("another 1");
-    const auto it = map.insert_or_assign(std::move(k), std::move(v));
+    const auto& [it, inserted] =
+        map.insert_or_assign(std::move(k), std::move(v));
+    EXPECT_FALSE(inserted);
     EXPECT_EQ(it->first, 1);
     EXPECT_EQ(it->second, "another 1");
     EXPECT_EQ(k, 1);
@@ -1509,7 +1513,8 @@ TEST(SortedVectorTypes, TestInsertOrAssign) {
   {
     auto k = folly::make_optional<int>(2);
     auto v = folly::make_optional<std::string>("2");
-    const auto it = map.insert_or_assign(k, v);
+    const auto& [it, inserted] = map.insert_or_assign(k, v);
+    EXPECT_TRUE(inserted);
     EXPECT_EQ(it->first, 2);
     EXPECT_EQ(it->second, "2");
     EXPECT_EQ(k, 2);