Creation of LTS branch "lts_2019_08_08"20190808

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  - 27c30ec671cb7b5ba84c4e79feff7fd0b0ac6338 Avoid undefined behavior when nullptr is passed to memcpy... by Roman Gershman <romange@gmail.com>
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  - 253eb7416421661873afbaa33828a850db978541 [CMake] Set correct flags for clang-cl (#278) by Loo Rong Jie <loorongjie@gmail.com>
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  - c1cecb25a94c075725e9d2640f6b978a8f61957b Implement Span::first and Span::last from C++20 (#274) by Girts <girtsf@users.noreply.github.com>
  - 38b704384cd2f17590b3922b97744be0b43622c9 Changed HTTP URLs to HTTPS where possible (#270) by nik7273 <nik8470@gmail.com>
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  - 89ea0c5ff34aaa5855cfc7aa41f323b8a0ef0ede Merge pull request #255 from uilianries/hotfix/conan by ahedberg <ahedberg@google.com>
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  - 6b4201f9ef650637510a21b8d6cbcc3bee4a606f Fix GCC8 warnings by Boris Staletic <boris.staletic@gmail.com>
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  - 9449ae94397f2fd683851348e25ed8c93f75b3b9 Merge pull request #243 from ThomsonTan/FixIntrinsic by Alex Strelnikov <strel@google.com>
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  - 3e2e9b5557e76d098de4b8a2a659125b98ca519b Merge pull request #231 from uilianries/feature/conan by Mark Barolak <mbxx@users.noreply.github.com>
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GitOrigin-RevId: 9ee91d3e430fb33a4590486573792eb0fa146c2d
Change-Id: Ia06e548bc106cc9d136f6c65714be6645317aced

12 files changed, 535 insertions, 186 deletions

diff --git a/absl/hash/BUILD.bazel b/absl/hash/BUILD.bazel
index 4f7c94ce..8c2daf70 100644
--- a/absl/hash/BUILD.bazel
+++ b/absl/hash/BUILD.bazel
@@ -5,7 +5,7 @@
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-#      http://www.apache.org/licenses/LICENSE-2.0
+#      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,
@@ -15,8 +15,9 @@
 #
 
 load(
-    "//absl:copts.bzl",
+    "//absl:copts/configure_copts.bzl",
     "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
     "ABSL_TEST_COPTS",
 )
 
@@ -32,6 +33,7 @@ cc_library(
     ],
     hdrs = ["hash.h"],
     copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":city",
         "//absl/base:core_headers",
@@ -50,6 +52,7 @@ cc_library(
     name = "hash_testing",
     testonly = 1,
     hdrs = ["hash_testing.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":spy_hash_state",
         "//absl/meta:type_traits",
@@ -63,6 +66,7 @@ cc_test(
     name = "hash_test",
     srcs = ["hash_test.cc"],
     copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":hash",
         ":hash_testing",
@@ -80,6 +84,7 @@ cc_library(
     testonly = 1,
     hdrs = ["internal/spy_hash_state.h"],
     copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
     deps = [
         ":hash",
@@ -95,6 +100,7 @@ cc_library(
         "internal/city.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -106,6 +112,7 @@ cc_test(
     name = "city_test",
     srcs = ["internal/city_test.cc"],
     copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":city",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/hash/CMakeLists.txt b/absl/hash/CMakeLists.txt
index 8f97d7cc..febc551f 100644
--- a/absl/hash/CMakeLists.txt
+++ b/absl/hash/CMakeLists.txt
@@ -5,7 +5,7 @@
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-#      http://www.apache.org/licenses/LICENSE-2.0
+#      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,
@@ -43,6 +43,8 @@ absl_cc_library(
     hash_testing
   HDRS
     "hash_testing.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
   DEPS
     absl::spy_hash_state
     absl::meta
@@ -56,7 +58,9 @@ absl_cc_test(
   NAME
     hash_test
   SRCS
-   "hash_test.cc"
+    "hash_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
   DEPS
     absl::hash
     absl::hash_testing
diff --git a/absl/hash/hash.h b/absl/hash/hash.h
index 2c8982b8..d36f0960 100644
--- a/absl/hash/hash.h
+++ b/absl/hash/hash.h
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -36,25 +36,34 @@
 // framework by simply combining its state with the state of known, hashable
 // types. Hashing of that combined state is separately done by `absl::Hash`.
 //
+// One should assume that a hash algorithm is chosen randomly at the start of
+// each process.  E.g., absl::Hash<int>()(9) in one process and
+// absl::Hash<int>()(9) in another process are likely to differ.
+//
 // Example:
 //
-//   // Suppose we have a class `Circle` for which we want to add hashing
+//   // Suppose we have a class `Circle` for which we want to add hashing:
 //   class Circle {
-//     public:
-//       ...
-//     private:
-//       std::pair<int, int> center_;
-//       int radius_;
-//     };
-//
-//   // To add hashing support to `Circle`, we simply need to add an ordinary
-//   // function `AbslHashValue()`, and return the combined hash state of the
-//   // existing hash state and the class state:
+//    public:
+//     ...
+//    private:
+//     std::pair<int, int> center_;
+//     int radius_;
+//   };
 //
+//   // To add hashing support to `Circle`, we simply need to add a free
+//   // (non-member) function `AbslHashValue()`, and return the combined hash
+//   // state of the existing hash state and the class state. You can add such a
+//   // free function using a friend declaration within the body of the class:
+//   class Circle {
+//    public:
+//     ...
 //     template <typename H>
 //     friend H AbslHashValue(H h, const Circle& c) {
 //       return H::combine(std::move(h), c.center_, c.radius_);
 //     }
+//     ...
+//   };
 //
 // For more information, see Adding Type Support to `absl::Hash` below.
 //
@@ -64,7 +73,7 @@
 #include "absl/hash/internal/hash.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 
 // -----------------------------------------------------------------------------
 // `absl::Hash`
@@ -236,7 +245,7 @@ using Hash = absl::hash_internal::Hash<T>;
 //     }
 //    private:
 //     virtual void HashValue(absl::HashState state) const = 0;
-//  };
+//   };
 //
 //   class Impl : Interface {
 //    private:
@@ -244,7 +253,7 @@ using Hash = absl::hash_internal::Hash<T>;
 //       absl::HashState::combine(std::move(state), v1_, v2_);
 //     }
 //     int v1_;
-//     string v2_;
+//     std::string v2_;
 //   };
 class HashState : public hash_internal::HashStateBase<HashState> {
  public:
@@ -309,6 +318,7 @@ class HashState : public hash_internal::HashStateBase<HashState> {
   void (*combine_contiguous_)(void*, const unsigned char*, size_t);
 };
 
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
+
 #endif  // ABSL_HASH_HASH_H_
diff --git a/absl/hash/hash_test.cc b/absl/hash/hash_test.cc
index 4a1a98d5..2a4e2262 100644
--- a/absl/hash/hash_test.cc
+++ b/absl/hash/hash_test.cc
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -15,6 +15,7 @@
 #include "absl/hash/hash.h"
 
 #include <array>
+#include <bitset>
 #include <cstring>
 #include <deque>
 #include <forward_list>
@@ -50,7 +51,7 @@ using absl::hash_internal::SpyHashState;
 template <typename T>
 class HashValueIntTest : public testing::Test {
 };
-TYPED_TEST_CASE_P(HashValueIntTest);
+TYPED_TEST_SUITE_P(HashValueIntTest);
 
 template <typename T>
 SpyHashState SpyHash(const T& value) {
@@ -84,11 +85,349 @@ using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t, uint
                                 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);
+  }
+};
+
+TEST(HashValueTest, Strings) {
+  EXPECT_TRUE((is_hashable<std::string>::value));
+
+  const std::string small = "foo";
+  const std::string dup = "foofoo";
+  const std::string large = "large";
+  const std::string huge = std::string(5000, 'a');
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::string(), absl::string_view(),
+      std::string(""), absl::string_view(""),
+      std::string(small), absl::string_view(small),
+      std::string(dup), absl::string_view(dup),
+      std::string(large), absl::string_view(large),
+      std::string(huge), absl::string_view(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(std::string("")), t(absl::string_view("")),
+      t(std::string(small)), t(absl::string_view(small)),
+      t(std::string(dup)), t(absl::string_view(dup)),
+      t(std::string(large)), t(absl::string_view(large)),
+      t(std::string(huge)), t(absl::string_view(huge)))));
+
+  // Make sure that hashing a `const char*` does not use its std::string-value.
+  EXPECT_NE(SpyHash(static_cast<const char*>("ABC")),
+            SpyHash(absl::string_view("ABC")));
+}
+
+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
+// implentation 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(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"}})));
+}
+
 template <typename T, typename = void>
-struct IsHashCallble : std::false_type {};
+struct IsHashCallable : std::false_type {};
 
 template <typename T>
-struct IsHashCallble<T, absl::void_t<decltype(std::declval<absl::Hash<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>
@@ -105,10 +444,11 @@ TEST(IsHashableTest, ValidHash) {
   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(IsHashCallble<int>::value);
+  EXPECT_TRUE(IsHashCallable<int>::value);
   EXPECT_TRUE(IsAggregateInitializable<absl::Hash<int>>::value);
 }
-#if ABSL_HASH_INTERNAL_CAN_POISON_ && !defined(__APPLE__)
+
+#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
 TEST(IsHashableTest, PoisonHash) {
   struct X {};
   EXPECT_FALSE((is_hashable<X>::value));
@@ -117,10 +457,10 @@ TEST(IsHashableTest, PoisonHash) {
   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(IsHashCallble<X>::value);
+  EXPECT_FALSE(IsHashCallable<X>::value);
   EXPECT_FALSE(IsAggregateInitializable<absl::Hash<X>>::value);
 }
-#endif  // ABSL_HASH_INTERNAL_CAN_POISON_
+#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
 
 // Hashable types
 //
@@ -129,7 +469,7 @@ TEST(IsHashableTest, PoisonHash) {
 struct NoOp {
   template <typename HashCode>
   friend HashCode AbslHashValue(HashCode h, NoOp n) {
-    return std::move(h);
+    return h;
   }
 };
 
@@ -159,8 +499,16 @@ struct CombineVariadic {
                              Int(4));
   }
 };
+enum class InvokeTag {
+  kUniquelyRepresented,
+  kHashValue,
+#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  kLegacyHash,
+#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  kStdHash,
+  kNone
+};
 
-using InvokeTag = absl::hash_internal::InvokeHashTag;
 template <InvokeTag T>
 using InvokeTagConstant = std::integral_constant<InvokeTag, T>;
 
@@ -175,6 +523,7 @@ struct MinTag<a> : InvokeTagConstant<a> {};
 
 template <InvokeTag... Tags>
 struct CustomHashType {
+  explicit CustomHashType(size_t val) : value(val) {}
   size_t value;
 };
 
@@ -195,7 +544,7 @@ H AbslHashValue(H state, CustomHashType<Tags...> t) {
 }  // namespace
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 template <InvokeTag... Tags>
 struct is_uniquely_represented<
@@ -203,7 +552,7 @@ struct is_uniquely_represented<
     typename EnableIfContained<InvokeTag::kUniquelyRepresented, Tags...>::type>
     : std::true_type {};
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
 
 #if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
@@ -243,17 +592,17 @@ void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>, T...) {
   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}));
+  EXPECT_EQ(SpyHash(type(7)), SpyHash(size_t{7 + offset}));
 }
 
 void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>) {
-#if ABSL_HASH_INTERNAL_CAN_POISON_
+#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_HASH_INTERNAL_CAN_POISON_
+#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
 }
 
 template <InvokeTag Tag, typename... T>
@@ -275,7 +624,7 @@ TEST(HashTest, NoOpsAreEquivalent) {
 template <typename T>
 class HashIntTest : public testing::Test {
 };
-TYPED_TEST_CASE_P(HashIntTest);
+TYPED_TEST_SUITE_P(HashIntTest);
 
 TYPED_TEST_P(HashIntTest, BasicUsage) {
   EXPECT_NE(Hash<NoOp>()({}), Hash<TypeParam>()(0));
@@ -354,7 +703,8 @@ TEST(HashTest, HashNonUniquelyRepresentedType) {
 }
 
 TEST(HashTest, StandardHashContainerUsage) {
-  std::unordered_map<int, std::string, Hash<int>> map = {{0, "foo"}, { 42, "bar" }};
+  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());
@@ -424,4 +774,24 @@ TEST(HashTest, TypeErased) {
             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
diff --git a/absl/hash/hash_testing.h b/absl/hash/hash_testing.h
index 1c4db26a..6e39028f 100644
--- a/absl/hash/hash_testing.h
+++ b/absl/hash/hash_testing.h
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -28,7 +28,7 @@
 #include "absl/types/variant.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 
 // Run the absl::Hash algorithm over all the elements passed in and verify that
 // their hash expansion is congruent with their `==` operator.
@@ -191,7 +191,9 @@ VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
   struct Info {
     const V& value;
     size_t index;
-    std::string ToString() const { return absl::visit(PrintVisitor{index}, value); }
+    std::string ToString() const {
+      return absl::visit(PrintVisitor{index}, value);
+    }
     SpyHashState expand() const { return absl::visit(ExpandVisitor{}, value); }
   };
 
@@ -370,7 +372,7 @@ VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
       equals);
 }
 
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
 
 #endif  // ABSL_HASH_HASH_TESTING_H_
diff --git a/absl/hash/internal/city.cc b/absl/hash/internal/city.cc
index 5c076fb5..c7ad1591 100644
--- a/absl/hash/internal/city.cc
+++ b/absl/hash/internal/city.cc
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -30,7 +30,7 @@
 #include "absl/base/optimization.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 #ifdef ABSL_IS_BIG_ENDIAN
@@ -342,5 +342,5 @@ uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0,
 }
 
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
diff --git a/absl/hash/internal/city.h b/absl/hash/internal/city.h
index 46c18ffa..7586ba08 100644
--- a/absl/hash/internal/city.h
+++ b/absl/hash/internal/city.h
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-// http://code.google.com/p/cityhash/
+// https://code.google.com/p/cityhash/
 //
 // This file provides a few functions for hashing strings.  All of them are
 // high-quality functions in the sense that they pass standard tests such
@@ -49,9 +49,8 @@
 #include <stdlib.h>  // for size_t.
 #include <utility>
 
-
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 typedef std::pair<uint64_t, uint64_t> uint128;
@@ -88,7 +87,7 @@ inline uint64_t Hash128to64(const uint128 &x) {
 }
 
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_CITY_H_
diff --git a/absl/hash/internal/city_test.cc b/absl/hash/internal/city_test.cc
index f305ed9e..1b9373c2 100644
--- a/absl/hash/internal/city_test.cc
+++ b/absl/hash/internal/city_test.cc
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -20,7 +20,7 @@
 #include "gtest/gtest.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
@@ -591,5 +591,5 @@ TEST(CityHashTest, Unchanging) {
 }
 
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
diff --git a/absl/hash/internal/hash.cc b/absl/hash/internal/hash.cc
index 3e553625..087b389b 100644
--- a/absl/hash/internal/hash.cc
+++ b/absl/hash/internal/hash.cc
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -15,11 +15,11 @@
 #include "absl/hash/internal/hash.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 ABSL_CONST_INIT const void* const CityHashState::kSeed = &kSeed;
 
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index a51ca954..81f1edf8 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -50,7 +50,7 @@
 #include "absl/hash/internal/city.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 // HashStateBase
@@ -222,7 +222,9 @@ typename std::enable_if<std::is_enum<Enum>::value, H>::type AbslHashValue(
 }
 // AbslHashValue() for hashing floating-point values
 template <typename H, typename Float>
-typename std::enable_if<std::is_floating_point<Float>::value, H>::type
+typename std::enable_if<std::is_same<Float, float>::value ||
+                            std::is_same<Float, double>::value,
+                        H>::type
 AbslHashValue(H hash_state, Float value) {
   return hash_internal::hash_bytes(std::move(hash_state),
                                    value == 0 ? 0 : value);
@@ -232,8 +234,9 @@ AbslHashValue(H hash_state, Float value) {
 // For example, in x86 sizeof(long double)==16 but it only really uses 80-bits
 // of it. This means we can't use hash_bytes on a long double and have to
 // convert it to something else first.
-template <typename H>
-H AbslHashValue(H hash_state, long double value) {
+template <typename H, typename LongDouble>
+typename std::enable_if<std::is_same<LongDouble, long double>::value, H>::type
+AbslHashValue(H hash_state, LongDouble value) {
   const int category = std::fpclassify(value);
   switch (category) {
     case FP_INFINITE:
@@ -265,7 +268,12 @@ H AbslHashValue(H hash_state, long double value) {
 // AbslHashValue() for hashing pointers
 template <typename H, typename T>
 H AbslHashValue(H hash_state, T* ptr) {
-  return hash_internal::hash_bytes(std::move(hash_state), ptr);
+  auto v = reinterpret_cast<uintptr_t>(ptr);
+  // Due to alignment, pointers tend to have low bits as zero, and the next few
+  // bits follow a pattern since they are also multiples of some base value.
+  // Mixing the pointer twice helps prevent stuck low bits for certain alignment
+  // values.
+  return H::combine(std::move(hash_state), v, v);
 }
 
 // AbslHashValue() for hashing nullptr_t
@@ -528,53 +536,22 @@ hash_range_or_bytes(H hash_state, const T* data, size_t size) {
   return hash_state;
 }
 
-// InvokeHashTag
-//
-// InvokeHash(H, const T&) invokes the appropriate hash implementation for a
-// hasher of type `H` and a value of type `T`. If `T` is not hashable, there
-// will be no matching overload of InvokeHash().
-// Note: Some platforms (eg MSVC) do not support the detect idiom on
-// std::hash. In those platforms the last fallback will be std::hash and
-// InvokeHash() will always have a valid overload even if std::hash<T> is not
-// valid.
-//
-// We try the following options in order:
-//   * If is_uniquely_represented, hash bytes directly.
-//   * ADL AbslHashValue(H, const T&) call.
-//   * std::hash<T>
-
-// In MSVC we can't probe std::hash or stdext::hash because it triggers a
-// static_assert instead of failing substitution.
-#if defined(_MSC_VER)
-#define ABSL_HASH_INTERNAL_CAN_POISON_ 0
-#else   // _MSC_VER
-#define ABSL_HASH_INTERNAL_CAN_POISON_ 1
-#endif  // _MSC_VER
-
 #if defined(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE) && \
-    ABSL_HASH_INTERNAL_CAN_POISON_
+    ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
 #define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 1
 #else
 #define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 0
 #endif
 
-enum class InvokeHashTag {
-  kUniquelyRepresented,
-  kHashValue,
-#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-  kLegacyHash,
-#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-  kStdHash,
-  kNone
-};
-
 // HashSelect
 //
 // Type trait to select the appropriate hash implementation to use.
-// HashSelect<T>::value is an instance of InvokeHashTag that indicates the best
-// available hashing mechanism.
-// See `Note` above about MSVC.
-template <typename T>
+// HashSelect::type<T> will give the proper hash implementation, to be invoked
+// as:
+//   HashSelect::type<T>::Invoke(state, value)
+// Also, HashSelect::type<T>::value is a boolean equal to `true` if there is a
+// valid `Invoke` function. Types that are not hashable will have a ::value of
+// `false`.
 struct HashSelect {
  private:
   struct State : HashStateBase<State> {
@@ -583,95 +560,75 @@ struct HashSelect {
     using State::HashStateBase::combine_contiguous;
   };
 
-  // `Probe<V, Tag>::value` evaluates to `V<T>::value` if it is a valid
-  // expression, and `false` otherwise.
-  // `Probe<V, Tag>::tag` always evaluates to `Tag`.
-  template <template <typename> class V, InvokeHashTag Tag>
-  struct Probe {
-   private:
-    template <typename U, typename std::enable_if<V<U>::value, int>::type = 0>
-    static std::true_type Test(int);
-    template <typename U>
-    static std::false_type Test(char);
-
-   public:
-    static constexpr InvokeHashTag kTag = Tag;
-    static constexpr bool value = decltype(
-        Test<absl::remove_const_t<absl::remove_reference_t<T>>>(0))::value;
+  struct UniquelyRepresentedProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value)
+        -> absl::enable_if_t<is_uniquely_represented<T>::value, H> {
+      return hash_internal::hash_bytes(std::move(state), value);
+    }
   };
 
-  template <typename U>
-  using ProbeUniquelyRepresented = is_uniquely_represented<U>;
-
-  template <typename U>
-  using ProbeHashValue =
-      std::is_same<State, decltype(AbslHashValue(std::declval<State>(),
-                                                 std::declval<const U&>()))>;
+  struct HashValueProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value) -> absl::enable_if_t<
+        std::is_same<H,
+                     decltype(AbslHashValue(std::move(state), value))>::value,
+        H> {
+      return AbslHashValue(std::move(state), value);
+    }
+  };
 
+  struct LegacyHashProbe {
 #if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-  template <typename U>
-  using ProbeLegacyHash =
-      std::is_convertible<decltype(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<
-                                   U>()(std::declval<const U&>())),
-                          size_t>;
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value) -> absl::enable_if_t<
+        std::is_convertible<
+            decltype(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>()(value)),
+            size_t>::value,
+        H> {
+      return hash_internal::hash_bytes(
+          std::move(state),
+          ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>{}(value));
+    }
 #endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  };
 
-  template <typename U>
-  using ProbeStdHash =
-#if ABSL_HASH_INTERNAL_CAN_POISON_
-      std::is_convertible<decltype(std::hash<U>()(std::declval<const U&>())),
-                          size_t>;
-#else   // ABSL_HASH_INTERNAL_CAN_POISON_
-      std::true_type;
-#endif  // ABSL_HASH_INTERNAL_CAN_POISON_
+  struct StdHashProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value)
+        -> absl::enable_if_t<type_traits_internal::IsHashable<T>::value, H> {
+      return hash_internal::hash_bytes(std::move(state), std::hash<T>{}(value));
+    }
+  };
 
-  template <typename U>
-  using ProbeNone = std::true_type;
+  template <typename Hash, typename T>
+  struct Probe : Hash {
+   private:
+    template <typename H, typename = decltype(H::Invoke(
+                              std::declval<State>(), std::declval<const T&>()))>
+    static std::true_type Test(int);
+    template <typename U>
+    static std::false_type Test(char);
+
+   public:
+    static constexpr bool value = decltype(Test<Hash>(0))::value;
+  };
 
  public:
   // Probe each implementation in order.
-  // disjunction provides short circuting wrt instantiation.
-  static constexpr InvokeHashTag value = absl::disjunction<
-      Probe<ProbeUniquelyRepresented, InvokeHashTag::kUniquelyRepresented>,
-      Probe<ProbeHashValue, InvokeHashTag::kHashValue>,
-#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-      Probe<ProbeLegacyHash, InvokeHashTag::kLegacyHash>,
-#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-      Probe<ProbeStdHash, InvokeHashTag::kStdHash>,
-      Probe<ProbeNone, InvokeHashTag::kNone>>::kTag;
+  // disjunction provides short circuiting wrt instantiation.
+  template <typename T>
+  using Apply = absl::disjunction<         //
+      Probe<UniquelyRepresentedProbe, T>,  //
+      Probe<HashValueProbe, T>,            //
+      Probe<LegacyHashProbe, T>,           //
+      Probe<StdHashProbe, T>,              //
+      std::false_type>;
 };
 
 template <typename T>
-struct is_hashable : std::integral_constant<bool, HashSelect<T>::value !=
-                                                      InvokeHashTag::kNone> {};
-
-template <typename H, typename T>
-absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kUniquelyRepresented,
-                  H>
-InvokeHash(H state, const T& value) {
-  return hash_internal::hash_bytes(std::move(state), value);
-}
-
-template <typename H, typename T>
-absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kHashValue, H>
-InvokeHash(H state, const T& value) {
-  return AbslHashValue(std::move(state), value);
-}
-
-#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-template <typename H, typename T>
-absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kLegacyHash, H>
-InvokeHash(H state, const T& value) {
-  return hash_internal::hash_bytes(
-      std::move(state), ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>{}(value));
-}
-#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
-
-template <typename H, typename T>
-absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kStdHash, H>
-InvokeHash(H state, const T& value) {
-  return hash_internal::hash_bytes(std::move(state), std::hash<T>{}(value));
-}
+struct is_hashable
+    : std::integral_constant<bool, HashSelect::template Apply<T>::value> {};
 
 // CityHashState
 class CityHashState : public HashStateBase<CityHashState> {
@@ -684,7 +641,8 @@ class CityHashState : public HashStateBase<CityHashState> {
 #endif  // ABSL_HAVE_INTRINSIC_INT128
 
   static constexpr uint64_t kMul =
-      sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51} : uint64_t{0x9ddfea08eb382d69};
+      sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51}
+                          : uint64_t{0x9ddfea08eb382d69};
 
   template <typename T>
   using IntegralFastPath =
@@ -881,7 +839,8 @@ struct Hash
 template <typename H>
 template <typename T, typename... Ts>
 H HashStateBase<H>::combine(H state, const T& value, const Ts&... values) {
-  return H::combine(hash_internal::InvokeHash(std::move(state), value),
+  return H::combine(hash_internal::HashSelect::template Apply<T>::Invoke(
+                        std::move(state), value),
                     values...);
 }
 
@@ -892,7 +851,7 @@ H HashStateBase<H>::combine_contiguous(H state, const T* data, size_t size) {
   return hash_internal::hash_range_or_bytes(std::move(state), data, size);
 }
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_HASH_H_
diff --git a/absl/hash/internal/print_hash_of.cc b/absl/hash/internal/print_hash_of.cc
index b6df31cc..c392125a 100644
--- a/absl/hash/internal/print_hash_of.cc
+++ b/absl/hash/internal/print_hash_of.cc
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
diff --git a/absl/hash/internal/spy_hash_state.h b/absl/hash/internal/spy_hash_state.h
index 1886d2ef..57cd70b2 100644
--- a/absl/hash/internal/spy_hash_state.h
+++ b/absl/hash/internal/spy_hash_state.h
@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//      http://www.apache.org/licenses/LICENSE-2.0
+//      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,
@@ -25,7 +25,7 @@
 #include "absl/strings/str_join.h"
 
 namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
 namespace hash_internal {
 
 // SpyHashState is an implementation of the HashState API that simply
@@ -40,8 +40,7 @@ namespace hash_internal {
 template <typename T>
 class SpyHashStateImpl : public HashStateBase<SpyHashStateImpl<T>> {
  public:
-  SpyHashStateImpl()
-      : error_(std::make_shared<absl::optional<std::string>>()) {
+  SpyHashStateImpl() : error_(std::make_shared<absl::optional<std::string>>()) {
     static_assert(std::is_void<T>::value, "");
   }
 
@@ -171,7 +170,6 @@ class SpyHashStateImpl : public HashStateBase<SpyHashStateImpl<T>> {
   // AbslHashValue directly (because the hash state type does not match).
   static bool direct_absl_hash_value_error_;
 
-
   std::vector<std::string> hash_representation_;
   // This is a shared_ptr because we want all instances of the particular
   // SpyHashState run to share the field. This way we can set the error for
@@ -201,7 +199,7 @@ bool RunOnStartup<f>::run = (f(), true);
 template <
     typename T, typename U,
     // Only trigger for when (T != U),
-    absl::enable_if_t<!std::is_same<T, U>::value, int> = 0,
+    typename = absl::enable_if_t<!std::is_same<T, U>::value>,
     // This statement works in two ways:
     //  - First, it instantiates RunOnStartup and forces the initialization of
     //    `run`, which set the global variable.
@@ -214,7 +212,7 @@ void AbslHashValue(SpyHashStateImpl<T>, const U&);
 using SpyHashState = SpyHashStateImpl<void>;
 
 }  // namespace hash_internal
-}  // inline namespace lts_2018_12_18
+}  // inline namespace lts_2019_08_08
 }  // namespace absl
 
 #endif  // ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_