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-// 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.
-
-#ifndef ABSL_HASH_HASH_TESTING_H_
-#define ABSL_HASH_HASH_TESTING_H_
-
-#include <initializer_list>
-#include <tuple>
-#include <type_traits>
-#include <vector>
-
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-#include "absl/hash/internal/spy_hash_state.h"
-#include "absl/meta/type_traits.h"
-#include "absl/strings/str_cat.h"
-#include "absl/types/variant.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-
-// Run the absl::Hash algorithm over all the elements passed in and verify that
-// their hash expansion is congruent with their `==` operator.
-//
-// It is used in conjunction with EXPECT_TRUE. Failures will output information
-// on what requirement failed and on which objects.
-//
-// Users should pass a collection of types as either an initializer list or a
-// container of cases.
-//
-//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-//       {v1, v2, ..., vN}));
-//
-//   std::vector<MyType> cases;
-//   // Fill cases...
-//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(cases));
-//
-// Users can pass a variety of types for testing heterogeneous lookup with
-// `std::make_tuple`:
-//
-//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-//       std::make_tuple(v1, v2, ..., vN)));
-//
-//
-// Ideally, the values passed should provide enough coverage of the `==`
-// operator and the AbslHashValue implementations.
-// For dynamically sized types, the empty state should usually be included in
-// the values.
-//
-// The function accepts an optional comparator function, in case that `==` is
-// not enough for the values provided.
-//
-// Usage:
-//
-//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
-//       std::make_tuple(v1, v2, ..., vN), MyCustomEq{}));
-//
-// It checks the following requirements:
-//   1. The expansion for a value is deterministic.
-//   2. For any two objects `a` and `b` in the sequence, if `a == b` evaluates
-//      to true, then their hash expansion must be equal.
-//   3. If `a == b` evaluates to false their hash expansion must be unequal.
-//   4. If `a == b` evaluates to false neither hash expansion can be a
-//      suffix of the other.
-//   5. AbslHashValue overloads should not be called by the user. They are only
-//      meant to be called by the framework. Users should call H::combine() and
-//      H::combine_contiguous().
-//   6. No moved-from instance of the hash state is used in the implementation
-//      of AbslHashValue.
-//
-// The values do not have to have the same type. This can be useful for
-// equivalent types that support heterogeneous lookup.
-//
-// A possible reason for breaking (2) is combining state in the hash expansion
-// that was not used in `==`.
-// For example:
-//
-// struct Bad2 {
-//   int a, b;
-//   template <typename H>
-//   friend H AbslHashValue(H state, Bad2 x) {
-//     // Uses a and b.
-//     return H::combine(std::move(state), x.a, x.b);
-//   }
-//   friend bool operator==(Bad2 x, Bad2 y) {
-//     // Only uses a.
-//     return x.a == y.a;
-//   }
-// };
-//
-// As for (3), breaking this usually means that there is state being passed to
-// the `==` operator that is not used in the hash expansion.
-// For example:
-//
-// struct Bad3 {
-//   int a, b;
-//   template <typename H>
-//   friend H AbslHashValue(H state, Bad3 x) {
-//     // Only uses a.
-//     return H::combine(std::move(state), x.a);
-//   }
-//   friend bool operator==(Bad3 x, Bad3 y) {
-//     // Uses a and b.
-//     return x.a == y.a && x.b == y.b;
-//   }
-// };
-//
-// Finally, a common way to break 4 is by combining dynamic ranges without
-// combining the size of the range.
-// For example:
-//
-// struct Bad4 {
-//   int *p, size;
-//   template <typename H>
-//   friend H AbslHashValue(H state, Bad4 x) {
-//     return H::combine_contiguous(std::move(state), x.p, x.p + x.size);
-//   }
-//   friend bool operator==(Bad4 x, Bad4 y) {
-//    // Compare two ranges for equality. C++14 code can instead use std::equal.
-//     return absl::equal(x.p, x.p + x.size, y.p, y.p + y.size);
-//   }
-// };
-//
-// An easy solution to this is to combine the size after combining the range,
-// like so:
-// template <typename H>
-// friend H AbslHashValue(H state, Bad4 x) {
-//   return H::combine(
-//       H::combine_contiguous(std::move(state), x.p, x.p + x.size), x.size);
-// }
-//
-template <int&... ExplicitBarrier, typename Container>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(const Container& values);
-
-template <int&... ExplicitBarrier, typename Container, typename Eq>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals);
-
-template <int&..., typename T>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values);
-
-template <int&..., typename T, typename Eq>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
-                                      Eq equals);
-
-namespace hash_internal {
-
-struct PrintVisitor {
-  size_t index;
-  template <typename T>
-  std::string operator()(const T* value) const {
-    return absl::StrCat("#", index, "(", testing::PrintToString(*value), ")");
-  }
-};
-
-template <typename Eq>
-struct EqVisitor {
-  Eq eq;
-  template <typename T, typename U>
-  bool operator()(const T* t, const U* u) const {
-    return eq(*t, *u);
-  }
-};
-
-struct ExpandVisitor {
-  template <typename T>
-  SpyHashState operator()(const T* value) const {
-    return SpyHashState::combine(SpyHashState(), *value);
-  }
-};
-
-template <typename Container, typename Eq>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
-  using V = typename Container::value_type;
-
-  struct Info {
-    const V& value;
-    size_t index;
-    std::string ToString() const {
-      return absl::visit(PrintVisitor{index}, value);
-    }
-    SpyHashState expand() const { return absl::visit(ExpandVisitor{}, value); }
-  };
-
-  using EqClass = std::vector<Info>;
-  std::vector<EqClass> classes;
-
-  // Gather the values in equivalence classes.
-  size_t i = 0;
-  for (const auto& value : values) {
-    EqClass* c = nullptr;
-    for (auto& eqclass : classes) {
-      if (absl::visit(EqVisitor<Eq>{equals}, value, eqclass[0].value)) {
-        c = &eqclass;
-        break;
-      }
-    }
-    if (c == nullptr) {
-      classes.emplace_back();
-      c = &classes.back();
-    }
-    c->push_back({value, i});
-    ++i;
-
-    // Verify potential errors captured by SpyHashState.
-    if (auto error = c->back().expand().error()) {
-      return testing::AssertionFailure() << *error;
-    }
-  }
-
-  if (classes.size() < 2) {
-    return testing::AssertionFailure()
-           << "At least two equivalence classes are expected.";
-  }
-
-  // We assume that equality is correctly implemented.
-  // Now we verify that AbslHashValue is also correctly implemented.
-
-  for (const auto& c : classes) {
-    // All elements of the equivalence class must have the same hash
-    // expansion.
-    const SpyHashState expected = c[0].expand();
-    for (const Info& v : c) {
-      if (v.expand() != v.expand()) {
-        return testing::AssertionFailure()
-               << "Hash expansion for " << v.ToString()
-               << " is non-deterministic.";
-      }
-      if (v.expand() != expected) {
-        return testing::AssertionFailure()
-               << "Values " << c[0].ToString() << " and " << v.ToString()
-               << " evaluate as equal but have an unequal hash expansion.";
-      }
-    }
-
-    // Elements from other classes must have different hash expansion.
-    for (const auto& c2 : classes) {
-      if (&c == &c2) continue;
-      const SpyHashState c2_hash = c2[0].expand();
-      switch (SpyHashState::Compare(expected, c2_hash)) {
-        case SpyHashState::CompareResult::kEqual:
-          return testing::AssertionFailure()
-                 << "Values " << c[0].ToString() << " and " << c2[0].ToString()
-                 << " evaluate as unequal but have an equal hash expansion.";
-        case SpyHashState::CompareResult::kBSuffixA:
-          return testing::AssertionFailure()
-                 << "Hash expansion of " << c2[0].ToString()
-                 << " is a suffix of the hash expansion of " << c[0].ToString()
-                 << ".";
-        case SpyHashState::CompareResult::kASuffixB:
-          return testing::AssertionFailure()
-                 << "Hash expansion of " << c[0].ToString()
-                 << " is a suffix of the hash expansion of " << c2[0].ToString()
-                 << ".";
-        case SpyHashState::CompareResult::kUnequal:
-          break;
-      }
-    }
-  }
-  return testing::AssertionSuccess();
-}
-
-template <typename... T>
-struct TypeSet {
-  template <typename U, bool = disjunction<std::is_same<T, U>...>::value>
-  struct Insert {
-    using type = TypeSet<U, T...>;
-  };
-  template <typename U>
-  struct Insert<U, true> {
-    using type = TypeSet;
-  };
-
-  template <template <typename...> class C>
-  using apply = C<T...>;
-};
-
-template <typename... T>
-struct MakeTypeSet : TypeSet<> {};
-template <typename T, typename... Ts>
-struct MakeTypeSet<T, Ts...> : MakeTypeSet<Ts...>::template Insert<T>::type {};
-
-template <typename... T>
-using VariantForTypes = typename MakeTypeSet<
-    const typename std::decay<T>::type*...>::template apply<absl::variant>;
-
-template <typename Container>
-struct ContainerAsVector {
-  using V = absl::variant<const typename Container::value_type*>;
-  using Out = std::vector<V>;
-
-  static Out Do(const Container& values) {
-    Out out;
-    for (const auto& v : values) out.push_back(&v);
-    return out;
-  }
-};
-
-template <typename... T>
-struct ContainerAsVector<std::tuple<T...>> {
-  using V = VariantForTypes<T...>;
-  using Out = std::vector<V>;
-
-  template <size_t... I>
-  static Out DoImpl(const std::tuple<T...>& tuple, absl::index_sequence<I...>) {
-    return Out{&std::get<I>(tuple)...};
-  }
-
-  static Out Do(const std::tuple<T...>& values) {
-    return DoImpl(values, absl::index_sequence_for<T...>());
-  }
-};
-
-template <>
-struct ContainerAsVector<std::tuple<>> {
-  static std::vector<VariantForTypes<int>> Do(std::tuple<>) { return {}; }
-};
-
-struct DefaultEquals {
-  template <typename T, typename U>
-  bool operator()(const T& t, const U& u) const {
-    return t == u;
-  }
-};
-
-}  // namespace hash_internal
-
-template <int&..., typename Container>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(const Container& values) {
-  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
-      hash_internal::ContainerAsVector<Container>::Do(values),
-      hash_internal::DefaultEquals{});
-}
-
-template <int&..., typename Container, typename Eq>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
-  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
-      hash_internal::ContainerAsVector<Container>::Do(values), equals);
-}
-
-template <int&..., typename T>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values) {
-  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
-      hash_internal::ContainerAsVector<std::initializer_list<T>>::Do(values),
-      hash_internal::DefaultEquals{});
-}
-
-template <int&..., typename T, typename Eq>
-ABSL_MUST_USE_RESULT testing::AssertionResult
-VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
-                                      Eq equals) {
-  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
-      hash_internal::ContainerAsVector<std::initializer_list<T>>::Do(values),
-      equals);
-}
-
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#endif  // ABSL_HASH_HASH_TESTING_H_