Changes imported from Abseil "staging" branch:

- 989557e6b443a81b5ad9bd0d0c704edbe96c09c9 Make InlinedVector::ShiftRight update the vector's size -... by Jon Cohen <cohenjon@google.com>
  - ffc2e2a6f169bbfa823890f21d13e16110cd0206 Fix issues when passing references aliasing into an Inlin... by Jon Cohen <cohenjon@google.com>
  - 2fce2f87043f8c044889b4aab828e6edc20da0d9 In C++14 or later, alias absl::make_unique to std::make_u... by Abseil Team <absl-team@google.com>
  - cb83e95b486c59fd6acfa956e97f42253dd158bd Roll back change to avoid weak virtual table warnings (-W... by Abseil Team <absl-team@google.com>
  - fb4ea46062895cb9340166c9dcc61ec4467bd834 Avoid weak virtual table warnings (-Wweak-vtables) and re... by Abseil Team <absl-team@google.com>

GitOrigin-RevId: 989557e6b443a81b5ad9bd0d0c704edbe96c09c9
Change-Id: I6b8119c3f16e9d0cb9b5fd6e750502c9dad8e257

absl/container/inlined_vector_test.cc

@@ -14,6 +14,7 @@
 
 #include "absl/container/inlined_vector.h"
 
+#include <algorithm>
 #include <forward_list>
 #include <list>
 #include <memory>
@@ -569,6 +570,16 @@ TEST(IntVec, CopyConstructorAndAssignment) {
   }
 }
 
+TEST(IntVec, AliasingCopyAssignment) {
+  for (int len = 0; len < 20; ++len) {
+    IntVec original;
+    Fill(&original, len);
+    IntVec dup = original;
+    dup = dup;
+    EXPECT_EQ(dup, original);
+  }
+}
+
 TEST(IntVec, MoveConstructorAndAssignment) {
   for (int len = 0; len < 20; len++) {
     IntVec v_in;
@@ -606,6 +617,78 @@ TEST(IntVec, MoveConstructorAndAssignment) {
   }
 }
 
+class NotTriviallyDestructible {
+ public:
+  NotTriviallyDestructible() : p_(new int(1)) {}
+  explicit NotTriviallyDestructible(int i) : p_(new int(i)) {}
+
+  NotTriviallyDestructible(const NotTriviallyDestructible& other)
+      : p_(new int(*other.p_)) {}
+
+  NotTriviallyDestructible& operator=(const NotTriviallyDestructible& other) {
+    p_ = absl::make_unique<int>(*other.p_);
+    return *this;
+  }
+
+  bool operator==(const NotTriviallyDestructible& other) const {
+    return *p_ == *other.p_;
+  }
+
+ private:
+  std::unique_ptr<int> p_;
+};
+
+TEST(AliasingTest, Emplace) {
+  for (int i = 2; i < 20; ++i) {
+    absl::InlinedVector<NotTriviallyDestructible, 10> vec;
+    for (int j = 0; j < i; ++j) {
+      vec.push_back(NotTriviallyDestructible(j));
+    }
+    vec.emplace(vec.begin(), vec[0]);
+    EXPECT_EQ(vec[0], vec[1]);
+    vec.emplace(vec.begin() + i / 2, vec[i / 2]);
+    EXPECT_EQ(vec[i / 2], vec[i / 2 + 1]);
+    vec.emplace(vec.end() - 1, vec.back());
+    EXPECT_EQ(vec[vec.size() - 2], vec.back());
+  }
+}
+
+TEST(AliasingTest, InsertWithCount) {
+  for (int i = 1; i < 20; ++i) {
+    absl::InlinedVector<NotTriviallyDestructible, 10> vec;
+    for (int j = 0; j < i; ++j) {
+      vec.push_back(NotTriviallyDestructible(j));
+    }
+    for (int n = 0; n < 5; ++n) {
+      // We use back where we can because it's guaranteed to become invalidated
+      vec.insert(vec.begin(), n, vec.back());
+      auto b = vec.begin();
+      EXPECT_TRUE(
+          std::all_of(b, b + n, [&vec](const NotTriviallyDestructible& x) {
+            return x == vec.back();
+          }));
+
+      auto m_idx = vec.size() / 2;
+      vec.insert(vec.begin() + m_idx, n, vec.back());
+      auto m = vec.begin() + m_idx;
+      EXPECT_TRUE(
+          std::all_of(m, m + n, [&vec](const NotTriviallyDestructible& x) {
+            return x == vec.back();
+          }));
+
+      // We want distinct values so the equality test is meaningful,
+      // vec[vec.size() - 1] is also almost always invalidated.
+      auto old_e = vec.size() - 1;
+      auto val = vec[old_e];
+      vec.insert(vec.end(), n, vec[old_e]);
+      auto e = vec.begin() + old_e;
+      EXPECT_TRUE(std::all_of(
+          e, e + n,
+          [&val](const NotTriviallyDestructible& x) { return x == val; }));
+    }
+  }
+}
+
 TEST(OverheadTest, Storage) {
   // Check for size overhead.
   // In particular, ensure that std::allocator doesn't cost anything to store.