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-rw-r--r--third_party/abseil_cpp/absl/hash/hash_test.cc976
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diff --git a/third_party/abseil_cpp/absl/hash/hash_test.cc b/third_party/abseil_cpp/absl/hash/hash_test.cc
deleted file mode 100644
index 1d2e6cf0df44..000000000000
--- a/third_party/abseil_cpp/absl/hash/hash_test.cc
+++ /dev/null
@@ -1,976 +0,0 @@
-// Copyright 2018 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include "absl/hash/hash.h"
-
-#include <array>
-#include <bitset>
-#include <cstring>
-#include <deque>
-#include <forward_list>
-#include <functional>
-#include <iterator>
-#include <limits>
-#include <list>
-#include <map>
-#include <memory>
-#include <numeric>
-#include <random>
-#include <set>
-#include <string>
-#include <tuple>
-#include <type_traits>
-#include <unordered_map>
-#include <utility>
-#include <vector>
-
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-#include "absl/container/flat_hash_set.h"
-#include "absl/hash/hash_testing.h"
-#include "absl/hash/internal/spy_hash_state.h"
-#include "absl/meta/type_traits.h"
-#include "absl/numeric/int128.h"
-#include "absl/strings/cord_test_helpers.h"
-
-namespace {
-
-using absl::Hash;
-using absl::hash_internal::SpyHashState;
-
-template <typename T>
-class HashValueIntTest : public testing::Test {
-};
-TYPED_TEST_SUITE_P(HashValueIntTest);
-
-template <typename T>
-SpyHashState SpyHash(const T& value) {
-  return SpyHashState::combine(SpyHashState(), value);
-}
-
-// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
-// detect it.
-template <typename T>
-using is_hashable = std::is_default_constructible<absl::Hash<T>>;
-
-TYPED_TEST_P(HashValueIntTest, BasicUsage) {
-  EXPECT_TRUE((is_hashable<TypeParam>::value));
-
-  TypeParam n = 42;
-  EXPECT_EQ(SpyHash(n), SpyHash(TypeParam{42}));
-  EXPECT_NE(SpyHash(n), SpyHash(TypeParam{0}));
-  EXPECT_NE(SpyHash(std::numeric_limits<TypeParam>::max()),
-            SpyHash(std::numeric_limits<TypeParam>::min()));
-}
-
-TYPED_TEST_P(HashValueIntTest, FastPath) {
-  // Test the fast-path to make sure the values are the same.
-  TypeParam n = 42;
-  EXPECT_EQ(absl::Hash<TypeParam>{}(n),
-            absl::Hash<std::tuple<TypeParam>>{}(std::tuple<TypeParam>(n)));
-}
-
-REGISTER_TYPED_TEST_CASE_P(HashValueIntTest, BasicUsage, FastPath);
-using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t,
-                                uint32_t, uint64_t, size_t>;
-INSTANTIATE_TYPED_TEST_CASE_P(My, HashValueIntTest, IntTypes);
-
-enum LegacyEnum { kValue1, kValue2, kValue3 };
-
-enum class EnumClass { kValue4, kValue5, kValue6 };
-
-TEST(HashValueTest, EnumAndBool) {
-  EXPECT_TRUE((is_hashable<LegacyEnum>::value));
-  EXPECT_TRUE((is_hashable<EnumClass>::value));
-  EXPECT_TRUE((is_hashable<bool>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      LegacyEnum::kValue1, LegacyEnum::kValue2, LegacyEnum::kValue3)));
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      EnumClass::kValue4, EnumClass::kValue5, EnumClass::kValue6)));
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(true, false)));
-}
-
-TEST(HashValueTest, FloatingPoint) {
-  EXPECT_TRUE((is_hashable<float>::value));
-  EXPECT_TRUE((is_hashable<double>::value));
-  EXPECT_TRUE((is_hashable<long double>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(42.f, 0.f, -0.f, std::numeric_limits<float>::infinity(),
-                      -std::numeric_limits<float>::infinity())));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(42., 0., -0., std::numeric_limits<double>::infinity(),
-                      -std::numeric_limits<double>::infinity())));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      // Add some values with small exponent to test that NORMAL values also
-      // append their category.
-      .5L, 1.L, 2.L, 4.L, 42.L, 0.L, -0.L,
-      17 * static_cast<long double>(std::numeric_limits<double>::max()),
-      std::numeric_limits<long double>::infinity(),
-      -std::numeric_limits<long double>::infinity())));
-}
-
-TEST(HashValueTest, Pointer) {
-  EXPECT_TRUE((is_hashable<int*>::value));
-
-  int i;
-  int* ptr = &i;
-  int* n = nullptr;
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(&i, ptr, nullptr, ptr + 1, n)));
-}
-
-TEST(HashValueTest, PointerAlignment) {
-  // We want to make sure that pointer alignment will not cause bits to be
-  // stuck.
-
-  constexpr size_t kTotalSize = 1 << 20;
-  std::unique_ptr<char[]> data(new char[kTotalSize]);
-  constexpr size_t kLog2NumValues = 5;
-  constexpr size_t kNumValues = 1 << kLog2NumValues;
-
-  for (size_t align = 1; align < kTotalSize / kNumValues;
-       align < 8 ? align += 1 : align < 1024 ? align += 8 : align += 32) {
-    SCOPED_TRACE(align);
-    ASSERT_LE(align * kNumValues, kTotalSize);
-
-    size_t bits_or = 0;
-    size_t bits_and = ~size_t{};
-
-    for (size_t i = 0; i < kNumValues; ++i) {
-      size_t hash = absl::Hash<void*>()(data.get() + i * align);
-      bits_or |= hash;
-      bits_and &= hash;
-    }
-
-    // Limit the scope to the bits we would be using for Swisstable.
-    constexpr size_t kMask = (1 << (kLog2NumValues + 7)) - 1;
-    size_t stuck_bits = (~bits_or | bits_and) & kMask;
-    EXPECT_EQ(stuck_bits, 0) << "0x" << std::hex << stuck_bits;
-  }
-}
-
-TEST(HashValueTest, PairAndTuple) {
-  EXPECT_TRUE((is_hashable<std::pair<int, int>>::value));
-  EXPECT_TRUE((is_hashable<std::pair<const int&, const int&>>::value));
-  EXPECT_TRUE((is_hashable<std::tuple<int&, int&>>::value));
-  EXPECT_TRUE((is_hashable<std::tuple<int&&, int&&>>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::make_pair(0, 42), std::make_pair(0, 42), std::make_pair(42, 0),
-      std::make_pair(0, 0), std::make_pair(42, 42), std::make_pair(1, 42))));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(std::make_tuple(0, 0, 0), std::make_tuple(0, 0, 42),
-                      std::make_tuple(0, 23, 0), std::make_tuple(17, 0, 0),
-                      std::make_tuple(42, 0, 0), std::make_tuple(3, 9, 9),
-                      std::make_tuple(0, 0, -42))));
-
-  // Test that tuples of lvalue references work (so we need a few lvalues):
-  int a = 0, b = 1, c = 17, d = 23;
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::tie(a, a), std::tie(a, b), std::tie(b, c), std::tie(c, d))));
-
-  // Test that tuples of rvalue references work:
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::forward_as_tuple(0, 0, 0), std::forward_as_tuple(0, 0, 42),
-      std::forward_as_tuple(0, 23, 0), std::forward_as_tuple(17, 0, 0),
-      std::forward_as_tuple(42, 0, 0), std::forward_as_tuple(3, 9, 9),
-      std::forward_as_tuple(0, 0, -42))));
-}
-
-TEST(HashValueTest, CombineContiguousWorks) {
-  std::vector<std::tuple<int>> v1 = {std::make_tuple(1), std::make_tuple(3)};
-  std::vector<std::tuple<int>> v2 = {std::make_tuple(1), std::make_tuple(2)};
-
-  auto vh1 = SpyHash(v1);
-  auto vh2 = SpyHash(v2);
-  EXPECT_NE(vh1, vh2);
-}
-
-struct DummyDeleter {
-  template <typename T>
-  void operator() (T* ptr) {}
-};
-
-struct SmartPointerEq {
-  template <typename T, typename U>
-  bool operator()(const T& t, const U& u) const {
-    return GetPtr(t) == GetPtr(u);
-  }
-
-  template <typename T>
-  static auto GetPtr(const T& t) -> decltype(&*t) {
-    return t ? &*t : nullptr;
-  }
-
-  static std::nullptr_t GetPtr(std::nullptr_t) { return nullptr; }
-};
-
-TEST(HashValueTest, SmartPointers) {
-  EXPECT_TRUE((is_hashable<std::unique_ptr<int>>::value));
-  EXPECT_TRUE((is_hashable<std::unique_ptr<int, DummyDeleter>>::value));
-  EXPECT_TRUE((is_hashable<std::shared_ptr<int>>::value));
-
-  int i, j;
-  std::unique_ptr<int, DummyDeleter> unique1(&i);
-  std::unique_ptr<int, DummyDeleter> unique2(&i);
-  std::unique_ptr<int, DummyDeleter> unique_other(&j);
-  std::unique_ptr<int, DummyDeleter> unique_null;
-
-  std::shared_ptr<int> shared1(&i, DummyDeleter());
-  std::shared_ptr<int> shared2(&i, DummyDeleter());
-  std::shared_ptr<int> shared_other(&j, DummyDeleter());
-  std::shared_ptr<int> shared_null;
-
-  // Sanity check of the Eq function.
-  ASSERT_TRUE(SmartPointerEq{}(unique1, shared1));
-  ASSERT_FALSE(SmartPointerEq{}(unique1, shared_other));
-  ASSERT_TRUE(SmartPointerEq{}(unique_null, nullptr));
-  ASSERT_FALSE(SmartPointerEq{}(shared2, nullptr));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::forward_as_tuple(&i, nullptr,                    //
-                            unique1, unique2, unique_null,  //
-                            absl::make_unique<int>(),       //
-                            shared1, shared2, shared_null,  //
-                            std::make_shared<int>()),
-      SmartPointerEq{}));
-}
-
-TEST(HashValueTest, FunctionPointer) {
-  using Func = int (*)();
-  EXPECT_TRUE(is_hashable<Func>::value);
-
-  Func p1 = [] { return 2; }, p2 = [] { return 1; };
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(p1, p2, nullptr)));
-}
-
-struct WrapInTuple {
-  template <typename T>
-  std::tuple<int, T, size_t> operator()(const T& t) const {
-    return std::make_tuple(7, t, 0xdeadbeef);
-  }
-};
-
-absl::Cord FlatCord(absl::string_view sv) {
-  absl::Cord c(sv);
-  c.Flatten();
-  return c;
-}
-
-absl::Cord FragmentedCord(absl::string_view sv) {
-  if (sv.size() < 2) {
-    return absl::Cord(sv);
-  }
-  size_t halfway = sv.size() / 2;
-  std::vector<absl::string_view> parts = {sv.substr(0, halfway),
-                                          sv.substr(halfway)};
-  return absl::MakeFragmentedCord(parts);
-}
-
-TEST(HashValueTest, Strings) {
-  EXPECT_TRUE((is_hashable<std::string>::value));
-
-  const std::string small = "foo";
-  const std::string dup = "foofoo";
-  const std::string large = std::string(2048, 'x');  // multiple of chunk size
-  const std::string huge = std::string(5000, 'a');   // not a multiple
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(  //
-      std::string(), absl::string_view(), absl::Cord(),                     //
-      std::string(""), absl::string_view(""), absl::Cord(""),               //
-      std::string(small), absl::string_view(small), absl::Cord(small),      //
-      std::string(dup), absl::string_view(dup), absl::Cord(dup),            //
-      std::string(large), absl::string_view(large), absl::Cord(large),      //
-      std::string(huge), absl::string_view(huge), FlatCord(huge),           //
-      FragmentedCord(huge))));
-
-  // Also check that nested types maintain the same hash.
-  const WrapInTuple t{};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(  //
-      t(std::string()), t(absl::string_view()), t(absl::Cord()),            //
-      t(std::string("")), t(absl::string_view("")), t(absl::Cord("")),      //
-      t(std::string(small)), t(absl::string_view(small)),                   //
-          t(absl::Cord(small)),                                             //
-      t(std::string(dup)), t(absl::string_view(dup)), t(absl::Cord(dup)),   //
-      t(std::string(large)), t(absl::string_view(large)),                   //
-          t(absl::Cord(large)),                                             //
-      t(std::string(huge)), t(absl::string_view(huge)),                     //
-          t(FlatCord(huge)), t(FragmentedCord(huge)))));
-
-  // Make sure that hashing a `const char*` does not use its string-value.
-  EXPECT_NE(SpyHash(static_cast<const char*>("ABC")),
-            SpyHash(absl::string_view("ABC")));
-}
-
-TEST(HashValueTest, WString) {
-  EXPECT_TRUE((is_hashable<std::wstring>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::wstring(), std::wstring(L"ABC"), std::wstring(L"ABC"),
-      std::wstring(L"Some other different string"),
-      std::wstring(L"Iñtërnâtiônàlizætiøn"))));
-}
-
-TEST(HashValueTest, U16String) {
-  EXPECT_TRUE((is_hashable<std::u16string>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::u16string(), std::u16string(u"ABC"), std::u16string(u"ABC"),
-      std::u16string(u"Some other different string"),
-      std::u16string(u"Iñtërnâtiônàlizætiøn"))));
-}
-
-TEST(HashValueTest, U32String) {
-  EXPECT_TRUE((is_hashable<std::u32string>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      std::u32string(), std::u32string(U"ABC"), std::u32string(U"ABC"),
-      std::u32string(U"Some other different string"),
-      std::u32string(U"Iñtërnâtiônàlizætiøn"))));
-}
-
-TEST(HashValueTest, StdArray) {
-  EXPECT_TRUE((is_hashable<std::array<int, 3>>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(std::array<int, 3>{}, std::array<int, 3>{{0, 23, 42}})));
-}
-
-TEST(HashValueTest, StdBitset) {
-  EXPECT_TRUE((is_hashable<std::bitset<257>>::value));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      {std::bitset<2>("00"), std::bitset<2>("01"), std::bitset<2>("10"),
-       std::bitset<2>("11")}));
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      {std::bitset<5>("10101"), std::bitset<5>("10001"), std::bitset<5>()}));
-
-  constexpr int kNumBits = 256;
-  std::array<std::string, 6> bit_strings;
-  bit_strings.fill(std::string(kNumBits, '1'));
-  bit_strings[1][0] = '0';
-  bit_strings[2][1] = '0';
-  bit_strings[3][kNumBits / 3] = '0';
-  bit_strings[4][kNumBits - 2] = '0';
-  bit_strings[5][kNumBits - 1] = '0';
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      {std::bitset<kNumBits>(bit_strings[0].c_str()),
-       std::bitset<kNumBits>(bit_strings[1].c_str()),
-       std::bitset<kNumBits>(bit_strings[2].c_str()),
-       std::bitset<kNumBits>(bit_strings[3].c_str()),
-       std::bitset<kNumBits>(bit_strings[4].c_str()),
-       std::bitset<kNumBits>(bit_strings[5].c_str())}));
-}  // namespace
-
-template <typename T>
-class HashValueSequenceTest : public testing::Test {
-};
-TYPED_TEST_SUITE_P(HashValueSequenceTest);
-
-TYPED_TEST_P(HashValueSequenceTest, BasicUsage) {
-  EXPECT_TRUE((is_hashable<TypeParam>::value));
-
-  using ValueType = typename TypeParam::value_type;
-  auto a = static_cast<ValueType>(0);
-  auto b = static_cast<ValueType>(23);
-  auto c = static_cast<ValueType>(42);
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(TypeParam(), TypeParam{}, TypeParam{a, b, c},
-                      TypeParam{a, b}, TypeParam{b, c})));
-}
-
-REGISTER_TYPED_TEST_CASE_P(HashValueSequenceTest, BasicUsage);
-using IntSequenceTypes =
-    testing::Types<std::deque<int>, std::forward_list<int>, std::list<int>,
-                   std::vector<int>, std::vector<bool>, std::set<int>,
-                   std::multiset<int>>;
-INSTANTIATE_TYPED_TEST_CASE_P(My, HashValueSequenceTest, IntSequenceTypes);
-
-// Private type that only supports AbslHashValue to make sure our chosen hash
-// implementation is recursive within absl::Hash.
-// It uses std::abs() on the value to provide different bitwise representations
-// of the same logical value.
-struct Private {
-  int i;
-  template <typename H>
-  friend H AbslHashValue(H h, Private p) {
-    return H::combine(std::move(h), std::abs(p.i));
-  }
-
-  friend bool operator==(Private a, Private b) {
-    return std::abs(a.i) == std::abs(b.i);
-  }
-
-  friend std::ostream& operator<<(std::ostream& o, Private p) {
-    return o << p.i;
-  }
-};
-
-// Test helper for combine_piecewise_buffer.  It holds a string_view to the
-// buffer-to-be-hashed.  Its AbslHashValue specialization will split up its
-// contents at the character offsets requested.
-class PiecewiseHashTester {
- public:
-  // Create a hash view of a buffer to be hashed contiguously.
-  explicit PiecewiseHashTester(absl::string_view buf)
-      : buf_(buf), piecewise_(false), split_locations_() {}
-
-  // Create a hash view of a buffer to be hashed piecewise, with breaks at the
-  // given locations.
-  PiecewiseHashTester(absl::string_view buf, std::set<size_t> split_locations)
-      : buf_(buf),
-        piecewise_(true),
-        split_locations_(std::move(split_locations)) {}
-
-  template <typename H>
-  friend H AbslHashValue(H h, const PiecewiseHashTester& p) {
-    if (!p.piecewise_) {
-      return H::combine_contiguous(std::move(h), p.buf_.data(), p.buf_.size());
-    }
-    absl::hash_internal::PiecewiseCombiner combiner;
-    if (p.split_locations_.empty()) {
-      h = combiner.add_buffer(std::move(h), p.buf_.data(), p.buf_.size());
-      return combiner.finalize(std::move(h));
-    }
-    size_t begin = 0;
-    for (size_t next : p.split_locations_) {
-      absl::string_view chunk = p.buf_.substr(begin, next - begin);
-      h = combiner.add_buffer(std::move(h), chunk.data(), chunk.size());
-      begin = next;
-    }
-    absl::string_view last_chunk = p.buf_.substr(begin);
-    if (!last_chunk.empty()) {
-      h = combiner.add_buffer(std::move(h), last_chunk.data(),
-                              last_chunk.size());
-    }
-    return combiner.finalize(std::move(h));
-  }
-
- private:
-  absl::string_view buf_;
-  bool piecewise_;
-  std::set<size_t> split_locations_;
-};
-
-// Dummy object that hashes as two distinct contiguous buffers, "foo" followed
-// by "bar"
-struct DummyFooBar {
-  template <typename H>
-  friend H AbslHashValue(H h, const DummyFooBar&) {
-    const char* foo = "foo";
-    const char* bar = "bar";
-    h = H::combine_contiguous(std::move(h), foo, 3);
-    h = H::combine_contiguous(std::move(h), bar, 3);
-    return h;
-  }
-};
-
-TEST(HashValueTest, CombinePiecewiseBuffer) {
-  absl::Hash<PiecewiseHashTester> hash;
-
-  // Check that hashing an empty buffer through the piecewise API works.
-  EXPECT_EQ(hash(PiecewiseHashTester("")), hash(PiecewiseHashTester("", {})));
-
-  // Similarly, small buffers should give consistent results
-  EXPECT_EQ(hash(PiecewiseHashTester("foobar")),
-            hash(PiecewiseHashTester("foobar", {})));
-  EXPECT_EQ(hash(PiecewiseHashTester("foobar")),
-            hash(PiecewiseHashTester("foobar", {3})));
-
-  // But hashing "foobar" in pieces gives a different answer than hashing "foo"
-  // contiguously, then "bar" contiguously.
-  EXPECT_NE(hash(PiecewiseHashTester("foobar", {3})),
-            absl::Hash<DummyFooBar>()(DummyFooBar{}));
-
-  // Test hashing a large buffer incrementally, broken up in several different
-  // ways.  Arrange for breaks on and near the stride boundaries to look for
-  // off-by-one errors in the implementation.
-  //
-  // This test is run on a buffer that is a multiple of the stride size, and one
-  // that isn't.
-  for (size_t big_buffer_size : {1024 * 2 + 512, 1024 * 3}) {
-    SCOPED_TRACE(big_buffer_size);
-    std::string big_buffer;
-    for (int i = 0; i < big_buffer_size; ++i) {
-      // Arbitrary string
-      big_buffer.push_back(32 + (i * (i / 3)) % 64);
-    }
-    auto big_buffer_hash = hash(PiecewiseHashTester(big_buffer));
-
-    const int possible_breaks = 9;
-    size_t breaks[possible_breaks] = {1,    512,  1023, 1024, 1025,
-                                      1536, 2047, 2048, 2049};
-    for (unsigned test_mask = 0; test_mask < (1u << possible_breaks);
-         ++test_mask) {
-      SCOPED_TRACE(test_mask);
-      std::set<size_t> break_locations;
-      for (int j = 0; j < possible_breaks; ++j) {
-        if (test_mask & (1u << j)) {
-          break_locations.insert(breaks[j]);
-        }
-      }
-      EXPECT_EQ(
-          hash(PiecewiseHashTester(big_buffer, std::move(break_locations))),
-          big_buffer_hash);
-    }
-  }
-}
-
-TEST(HashValueTest, PrivateSanity) {
-  // Sanity check that Private is working as the tests below expect it to work.
-  EXPECT_TRUE(is_hashable<Private>::value);
-  EXPECT_NE(SpyHash(Private{0}), SpyHash(Private{1}));
-  EXPECT_EQ(SpyHash(Private{1}), SpyHash(Private{1}));
-}
-
-TEST(HashValueTest, Optional) {
-  EXPECT_TRUE(is_hashable<absl::optional<Private>>::value);
-
-  using O = absl::optional<Private>;
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(O{}, O{{1}}, O{{-1}}, O{{10}})));
-}
-
-TEST(HashValueTest, Variant) {
-  using V = absl::variant<Private, std::string>;
-  EXPECT_TRUE(is_hashable<V>::value);
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      V(Private{1}), V(Private{-1}), V(Private{2}), V("ABC"), V("BCD"))));
-
-#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
-  struct S {};
-  EXPECT_FALSE(is_hashable<absl::variant<S>>::value);
-#endif
-}
-
-TEST(HashValueTest, Maps) {
-  EXPECT_TRUE((is_hashable<std::map<int, std::string>>::value));
-
-  using M = std::map<int, std::string>;
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      M{}, M{{0, "foo"}}, M{{1, "foo"}}, M{{0, "bar"}}, M{{1, "bar"}},
-      M{{0, "foo"}, {42, "bar"}}, M{{1, "foo"}, {42, "bar"}},
-      M{{1, "foo"}, {43, "bar"}}, M{{1, "foo"}, {43, "baz"}})));
-
-  using MM = std::multimap<int, std::string>;
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      MM{}, MM{{0, "foo"}}, MM{{1, "foo"}}, MM{{0, "bar"}}, MM{{1, "bar"}},
-      MM{{0, "foo"}, {0, "bar"}}, MM{{0, "bar"}, {0, "foo"}},
-      MM{{0, "foo"}, {42, "bar"}}, MM{{1, "foo"}, {42, "bar"}},
-      MM{{1, "foo"}, {1, "foo"}, {43, "bar"}}, MM{{1, "foo"}, {43, "baz"}})));
-}
-
-TEST(HashValueTest, ReferenceWrapper) {
-  EXPECT_TRUE(is_hashable<std::reference_wrapper<Private>>::value);
-
-  Private p1{1}, p10{10};
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      p1, p10, std::ref(p1), std::ref(p10), std::cref(p1), std::cref(p10))));
-
-  EXPECT_TRUE(is_hashable<std::reference_wrapper<int>>::value);
-  int one = 1, ten = 10;
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
-      one, ten, std::ref(one), std::ref(ten), std::cref(one), std::cref(ten))));
-
-  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-      std::make_tuple(std::tuple<std::reference_wrapper<int>>(std::ref(one)),
-                      std::tuple<std::reference_wrapper<int>>(std::ref(ten)),
-                      std::tuple<int>(one), std::tuple<int>(ten))));
-}
-
-template <typename T, typename = void>
-struct IsHashCallable : std::false_type {};
-
-template <typename T>
-struct IsHashCallable<T, absl::void_t<decltype(std::declval<absl::Hash<T>>()(
-                            std::declval<const T&>()))>> : std::true_type {};
-
-template <typename T, typename = void>
-struct IsAggregateInitializable : std::false_type {};
-
-template <typename T>
-struct IsAggregateInitializable<T, absl::void_t<decltype(T{})>>
-    : std::true_type {};
-
-TEST(IsHashableTest, ValidHash) {
-  EXPECT_TRUE((is_hashable<int>::value));
-  EXPECT_TRUE(std::is_default_constructible<absl::Hash<int>>::value);
-  EXPECT_TRUE(std::is_copy_constructible<absl::Hash<int>>::value);
-  EXPECT_TRUE(std::is_move_constructible<absl::Hash<int>>::value);
-  EXPECT_TRUE(absl::is_copy_assignable<absl::Hash<int>>::value);
-  EXPECT_TRUE(absl::is_move_assignable<absl::Hash<int>>::value);
-  EXPECT_TRUE(IsHashCallable<int>::value);
-  EXPECT_TRUE(IsAggregateInitializable<absl::Hash<int>>::value);
-}
-
-#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
-TEST(IsHashableTest, PoisonHash) {
-  struct X {};
-  EXPECT_FALSE((is_hashable<X>::value));
-  EXPECT_FALSE(std::is_default_constructible<absl::Hash<X>>::value);
-  EXPECT_FALSE(std::is_copy_constructible<absl::Hash<X>>::value);
-  EXPECT_FALSE(std::is_move_constructible<absl::Hash<X>>::value);
-  EXPECT_FALSE(absl::is_copy_assignable<absl::Hash<X>>::value);
-  EXPECT_FALSE(absl::is_move_assignable<absl::Hash<X>>::value);
-  EXPECT_FALSE(IsHashCallable<X>::value);
-#if !defined(__GNUC__) || __GNUC__ < 9
-  // This doesn't compile on GCC 9.
-  EXPECT_FALSE(IsAggregateInitializable<absl::Hash<X>>::value);
-#endif
-}
-#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
-
-// Hashable types
-//
-// These types exist simply to exercise various AbslHashValue behaviors, so
-// they are named by what their AbslHashValue overload does.
-struct NoOp {
-  template <typename HashCode>
-  friend HashCode AbslHashValue(HashCode h, NoOp n) {
-    return h;
-  }
-};
-
-struct EmptyCombine {
-  template <typename HashCode>
-  friend HashCode AbslHashValue(HashCode h, EmptyCombine e) {
-    return HashCode::combine(std::move(h));
-  }
-};
-
-template <typename Int>
-struct CombineIterative {
-  template <typename HashCode>
-  friend HashCode AbslHashValue(HashCode h, CombineIterative c) {
-    for (int i = 0; i < 5; ++i) {
-      h = HashCode::combine(std::move(h), Int(i));
-    }
-    return h;
-  }
-};
-
-template <typename Int>
-struct CombineVariadic {
-  template <typename HashCode>
-  friend HashCode AbslHashValue(HashCode h, CombineVariadic c) {
-    return HashCode::combine(std::move(h), Int(0), Int(1), Int(2), Int(3),
-                             Int(4));
-  }
-};
-enum class InvokeTag {
-  kUniquelyRepresented,
-  kHashValue,
-#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-  kLegacyHash,
-#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-  kStdHash,
-  kNone
-};
-
-template <InvokeTag T>
-using InvokeTagConstant = std::integral_constant<InvokeTag, T>;
-
-template <InvokeTag... Tags>
-struct MinTag;
-
-template <InvokeTag a, InvokeTag b, InvokeTag... Tags>
-struct MinTag<a, b, Tags...> : MinTag<(a < b ? a : b), Tags...> {};
-
-template <InvokeTag a>
-struct MinTag<a> : InvokeTagConstant<a> {};
-
-template <InvokeTag... Tags>
-struct CustomHashType {
-  explicit CustomHashType(size_t val) : value(val) {}
-  size_t value;
-};
-
-template <InvokeTag allowed, InvokeTag... tags>
-struct EnableIfContained
-    : std::enable_if<absl::disjunction<
-          std::integral_constant<bool, allowed == tags>...>::value> {};
-
-template <
-    typename H, InvokeTag... Tags,
-    typename = typename EnableIfContained<InvokeTag::kHashValue, Tags...>::type>
-H AbslHashValue(H state, CustomHashType<Tags...> t) {
-  static_assert(MinTag<Tags...>::value == InvokeTag::kHashValue, "");
-  return H::combine(std::move(state),
-                    t.value + static_cast<int>(InvokeTag::kHashValue));
-}
-
-}  // namespace
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace hash_internal {
-template <InvokeTag... Tags>
-struct is_uniquely_represented<
-    CustomHashType<Tags...>,
-    typename EnableIfContained<InvokeTag::kUniquelyRepresented, Tags...>::type>
-    : std::true_type {};
-}  // namespace hash_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE {
-template <InvokeTag... Tags>
-struct hash<CustomHashType<Tags...>> {
-  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
-                                     InvokeTag::kLegacyHash, TagsIn...>::type>
-  size_t operator()(CustomHashType<TagsIn...> t) const {
-    static_assert(MinTag<Tags...>::value == InvokeTag::kLegacyHash, "");
-    return t.value + static_cast<int>(InvokeTag::kLegacyHash);
-  }
-};
-}  // namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE
-#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-
-namespace std {
-template <InvokeTag... Tags>  // NOLINT
-struct hash<CustomHashType<Tags...>> {
-  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
-                                     InvokeTag::kStdHash, TagsIn...>::type>
-  size_t operator()(CustomHashType<TagsIn...> t) const {
-    static_assert(MinTag<Tags...>::value == InvokeTag::kStdHash, "");
-    return t.value + static_cast<int>(InvokeTag::kStdHash);
-  }
-};
-}  // namespace std
-
-namespace {
-
-template <typename... T>
-void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>, T...) {
-  using type = CustomHashType<T::value...>;
-  SCOPED_TRACE(testing::PrintToString(std::vector<InvokeTag>{T::value...}));
-  EXPECT_TRUE(is_hashable<type>());
-  EXPECT_TRUE(is_hashable<const type>());
-  EXPECT_TRUE(is_hashable<const type&>());
-
-  const size_t offset = static_cast<int>(std::min({T::value...}));
-  EXPECT_EQ(SpyHash(type(7)), SpyHash(size_t{7 + offset}));
-}
-
-void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>) {
-#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
-  // is_hashable is false if we don't support any of the hooks.
-  using type = CustomHashType<>;
-  EXPECT_FALSE(is_hashable<type>());
-  EXPECT_FALSE(is_hashable<const type>());
-  EXPECT_FALSE(is_hashable<const type&>());
-#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
-}
-
-template <InvokeTag Tag, typename... T>
-void TestCustomHashType(InvokeTagConstant<Tag> tag, T... t) {
-  constexpr auto next = static_cast<InvokeTag>(static_cast<int>(Tag) + 1);
-  TestCustomHashType(InvokeTagConstant<next>(), tag, t...);
-  TestCustomHashType(InvokeTagConstant<next>(), t...);
-}
-
-TEST(HashTest, CustomHashType) {
-  TestCustomHashType(InvokeTagConstant<InvokeTag{}>());
-}
-
-TEST(HashTest, NoOpsAreEquivalent) {
-  EXPECT_EQ(Hash<NoOp>()({}), Hash<NoOp>()({}));
-  EXPECT_EQ(Hash<NoOp>()({}), Hash<EmptyCombine>()({}));
-}
-
-template <typename T>
-class HashIntTest : public testing::Test {
-};
-TYPED_TEST_SUITE_P(HashIntTest);
-
-TYPED_TEST_P(HashIntTest, BasicUsage) {
-  EXPECT_NE(Hash<NoOp>()({}), Hash<TypeParam>()(0));
-  EXPECT_NE(Hash<NoOp>()({}),
-            Hash<TypeParam>()(std::numeric_limits<TypeParam>::max()));
-  if (std::numeric_limits<TypeParam>::min() != 0) {
-    EXPECT_NE(Hash<NoOp>()({}),
-              Hash<TypeParam>()(std::numeric_limits<TypeParam>::min()));
-  }
-
-  EXPECT_EQ(Hash<CombineIterative<TypeParam>>()({}),
-            Hash<CombineVariadic<TypeParam>>()({}));
-}
-
-REGISTER_TYPED_TEST_CASE_P(HashIntTest, BasicUsage);
-using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t,
-                                uint32_t, uint64_t, size_t>;
-INSTANTIATE_TYPED_TEST_CASE_P(My, HashIntTest, IntTypes);
-
-struct StructWithPadding {
-  char c;
-  int i;
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, const StructWithPadding& s) {
-    return H::combine(std::move(hash_state), s.c, s.i);
-  }
-};
-
-static_assert(sizeof(StructWithPadding) > sizeof(char) + sizeof(int),
-              "StructWithPadding doesn't have padding");
-static_assert(std::is_standard_layout<StructWithPadding>::value, "");
-
-// This check has to be disabled because libstdc++ doesn't support it.
-// static_assert(std::is_trivially_constructible<StructWithPadding>::value, "");
-
-template <typename T>
-struct ArraySlice {
-  T* begin;
-  T* end;
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, const ArraySlice& slice) {
-    for (auto t = slice.begin; t != slice.end; ++t) {
-      hash_state = H::combine(std::move(hash_state), *t);
-    }
-    return hash_state;
-  }
-};
-
-TEST(HashTest, HashNonUniquelyRepresentedType) {
-  // Create equal StructWithPadding objects that are known to have non-equal
-  // padding bytes.
-  static const size_t kNumStructs = 10;
-  unsigned char buffer1[kNumStructs * sizeof(StructWithPadding)];
-  std::memset(buffer1, 0, sizeof(buffer1));
-  auto* s1 = reinterpret_cast<StructWithPadding*>(buffer1);
-
-  unsigned char buffer2[kNumStructs * sizeof(StructWithPadding)];
-  std::memset(buffer2, 255, sizeof(buffer2));
-  auto* s2 = reinterpret_cast<StructWithPadding*>(buffer2);
-  for (int i = 0; i < kNumStructs; ++i) {
-    SCOPED_TRACE(i);
-    s1[i].c = s2[i].c = '0' + i;
-    s1[i].i = s2[i].i = i;
-    ASSERT_FALSE(memcmp(buffer1 + i * sizeof(StructWithPadding),
-                        buffer2 + i * sizeof(StructWithPadding),
-                        sizeof(StructWithPadding)) == 0)
-        << "Bug in test code: objects do not have unequal"
-        << " object representations";
-  }
-
-  EXPECT_EQ(Hash<StructWithPadding>()(s1[0]), Hash<StructWithPadding>()(s2[0]));
-  EXPECT_EQ(Hash<ArraySlice<StructWithPadding>>()({s1, s1 + kNumStructs}),
-            Hash<ArraySlice<StructWithPadding>>()({s2, s2 + kNumStructs}));
-}
-
-TEST(HashTest, StandardHashContainerUsage) {
-  std::unordered_map<int, std::string, Hash<int>> map = {{0, "foo"},
-                                                         {42, "bar"}};
-
-  EXPECT_NE(map.find(0), map.end());
-  EXPECT_EQ(map.find(1), map.end());
-  EXPECT_NE(map.find(0u), map.end());
-}
-
-struct ConvertibleFromNoOp {
-  ConvertibleFromNoOp(NoOp) {}  // NOLINT(runtime/explicit)
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, ConvertibleFromNoOp) {
-    return H::combine(std::move(hash_state), 1);
-  }
-};
-
-TEST(HashTest, HeterogeneousCall) {
-  EXPECT_NE(Hash<ConvertibleFromNoOp>()(NoOp()),
-            Hash<NoOp>()(NoOp()));
-}
-
-TEST(IsUniquelyRepresentedTest, SanityTest) {
-  using absl::hash_internal::is_uniquely_represented;
-
-  EXPECT_TRUE(is_uniquely_represented<unsigned char>::value);
-  EXPECT_TRUE(is_uniquely_represented<int>::value);
-  EXPECT_FALSE(is_uniquely_represented<bool>::value);
-  EXPECT_FALSE(is_uniquely_represented<int*>::value);
-}
-
-struct IntAndString {
-  int i;
-  std::string s;
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, IntAndString int_and_string) {
-    return H::combine(std::move(hash_state), int_and_string.s,
-                      int_and_string.i);
-  }
-};
-
-TEST(HashTest, SmallValueOn64ByteBoundary) {
-  Hash<IntAndString>()(IntAndString{0, std::string(63, '0')});
-}
-
-struct TypeErased {
-  size_t n;
-
-  template <typename H>
-  friend H AbslHashValue(H hash_state, const TypeErased& v) {
-    v.HashValue(absl::HashState::Create(&hash_state));
-    return hash_state;
-  }
-
-  void HashValue(absl::HashState state) const {
-    absl::HashState::combine(std::move(state), n);
-  }
-};
-
-TEST(HashTest, TypeErased) {
-  EXPECT_TRUE((is_hashable<TypeErased>::value));
-  EXPECT_TRUE((is_hashable<std::pair<TypeErased, int>>::value));
-
-  EXPECT_EQ(SpyHash(TypeErased{7}), SpyHash(size_t{7}));
-  EXPECT_NE(SpyHash(TypeErased{7}), SpyHash(size_t{13}));
-
-  EXPECT_EQ(SpyHash(std::make_pair(TypeErased{7}, 17)),
-            SpyHash(std::make_pair(size_t{7}, 17)));
-}
-
-struct ValueWithBoolConversion {
-  operator bool() const { return false; }
-  int i;
-};
-
-}  // namespace
-namespace std {
-template <>
-struct hash<ValueWithBoolConversion> {
-  size_t operator()(ValueWithBoolConversion v) { return v.i; }
-};
-}  // namespace std
-
-namespace {
-
-TEST(HashTest, DoesNotUseImplicitConversionsToBool) {
-  EXPECT_NE(absl::Hash<ValueWithBoolConversion>()(ValueWithBoolConversion{0}),
-            absl::Hash<ValueWithBoolConversion>()(ValueWithBoolConversion{1}));
-}
-
-}  // namespace