Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 5615 insertions, 0 deletions

diff --git a/third_party/googletest/googlemock/include/gmock/gmock-matchers.h b/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
new file mode 100644
index 0000000000..b5f487b01c
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
@@ -0,0 +1,5615 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// The MATCHER* family of macros can be used in a namespace scope to
+// define custom matchers easily.
+//
+// Basic Usage
+// ===========
+//
+// The syntax
+//
+//   MATCHER(name, description_string) { statements; }
+//
+// defines a matcher with the given name that executes the statements,
+// which must return a bool to indicate if the match succeeds.  Inside
+// the statements, you can refer to the value being matched by 'arg',
+// and refer to its type by 'arg_type'.
+//
+// The description string documents what the matcher does, and is used
+// to generate the failure message when the match fails.  Since a
+// MATCHER() is usually defined in a header file shared by multiple
+// C++ source files, we require the description to be a C-string
+// literal to avoid possible side effects.  It can be empty, in which
+// case we'll use the sequence of words in the matcher name as the
+// description.
+//
+// For example:
+//
+//   MATCHER(IsEven, "") { return (arg % 2) == 0; }
+//
+// allows you to write
+//
+//   // Expects mock_foo.Bar(n) to be called where n is even.
+//   EXPECT_CALL(mock_foo, Bar(IsEven()));
+//
+// or,
+//
+//   // Verifies that the value of some_expression is even.
+//   EXPECT_THAT(some_expression, IsEven());
+//
+// If the above assertion fails, it will print something like:
+//
+//   Value of: some_expression
+//   Expected: is even
+//     Actual: 7
+//
+// where the description "is even" is automatically calculated from the
+// matcher name IsEven.
+//
+// Argument Type
+// =============
+//
+// Note that the type of the value being matched (arg_type) is
+// determined by the context in which you use the matcher and is
+// supplied to you by the compiler, so you don't need to worry about
+// declaring it (nor can you).  This allows the matcher to be
+// polymorphic.  For example, IsEven() can be used to match any type
+// where the value of "(arg % 2) == 0" can be implicitly converted to
+// a bool.  In the "Bar(IsEven())" example above, if method Bar()
+// takes an int, 'arg_type' will be int; if it takes an unsigned long,
+// 'arg_type' will be unsigned long; and so on.
+//
+// Parameterizing Matchers
+// =======================
+//
+// Sometimes you'll want to parameterize the matcher.  For that you
+// can use another macro:
+//
+//   MATCHER_P(name, param_name, description_string) { statements; }
+//
+// For example:
+//
+//   MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; }
+//
+// will allow you to write:
+//
+//   EXPECT_THAT(Blah("a"), HasAbsoluteValue(n));
+//
+// which may lead to this message (assuming n is 10):
+//
+//   Value of: Blah("a")
+//   Expected: has absolute value 10
+//     Actual: -9
+//
+// Note that both the matcher description and its parameter are
+// printed, making the message human-friendly.
+//
+// In the matcher definition body, you can write 'foo_type' to
+// reference the type of a parameter named 'foo'.  For example, in the
+// body of MATCHER_P(HasAbsoluteValue, value) above, you can write
+// 'value_type' to refer to the type of 'value'.
+//
+// We also provide MATCHER_P2, MATCHER_P3, ..., up to MATCHER_P$n to
+// support multi-parameter matchers.
+//
+// Describing Parameterized Matchers
+// =================================
+//
+// The last argument to MATCHER*() is a string-typed expression.  The
+// expression can reference all of the matcher's parameters and a
+// special bool-typed variable named 'negation'.  When 'negation' is
+// false, the expression should evaluate to the matcher's description;
+// otherwise it should evaluate to the description of the negation of
+// the matcher.  For example,
+//
+//   using testing::PrintToString;
+//
+//   MATCHER_P2(InClosedRange, low, hi,
+//       std::string(negation ? "is not" : "is") + " in range [" +
+//       PrintToString(low) + ", " + PrintToString(hi) + "]") {
+//     return low <= arg && arg <= hi;
+//   }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: is in range [4, 6]
+//   ...
+//   Expected: is not in range [2, 4]
+//
+// If you specify "" as the description, the failure message will
+// contain the sequence of words in the matcher name followed by the
+// parameter values printed as a tuple.  For example,
+//
+//   MATCHER_P2(InClosedRange, low, hi, "") { ... }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: in closed range (4, 6)
+//   ...
+//   Expected: not (in closed range (2, 4))
+//
+// Types of Matcher Parameters
+// ===========================
+//
+// For the purpose of typing, you can view
+//
+//   MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... }
+//
+// as shorthand for
+//
+//   template <typename p1_type, ..., typename pk_type>
+//   FooMatcherPk<p1_type, ..., pk_type>
+//   Foo(p1_type p1, ..., pk_type pk) { ... }
+//
+// When you write Foo(v1, ..., vk), the compiler infers the types of
+// the parameters v1, ..., and vk for you.  If you are not happy with
+// the result of the type inference, you can specify the types by
+// explicitly instantiating the template, as in Foo<long, bool>(5,
+// false).  As said earlier, you don't get to (or need to) specify
+// 'arg_type' as that's determined by the context in which the matcher
+// is used.  You can assign the result of expression Foo(p1, ..., pk)
+// to a variable of type FooMatcherPk<p1_type, ..., pk_type>.  This
+// can be useful when composing matchers.
+//
+// While you can instantiate a matcher template with reference types,
+// passing the parameters by pointer usually makes your code more
+// readable.  If, however, you still want to pass a parameter by
+// reference, be aware that in the failure message generated by the
+// matcher you will see the value of the referenced object but not its
+// address.
+//
+// Explaining Match Results
+// ========================
+//
+// Sometimes the matcher description alone isn't enough to explain why
+// the match has failed or succeeded.  For example, when expecting a
+// long string, it can be very helpful to also print the diff between
+// the expected string and the actual one.  To achieve that, you can
+// optionally stream additional information to a special variable
+// named result_listener, whose type is a pointer to class
+// MatchResultListener:
+//
+//   MATCHER_P(EqualsLongString, str, "") {
+//     if (arg == str) return true;
+//
+//     *result_listener << "the difference: "
+///                     << DiffStrings(str, arg);
+//     return false;
+//   }
+//
+// Overloading Matchers
+// ====================
+//
+// You can overload matchers with different numbers of parameters:
+//
+//   MATCHER_P(Blah, a, description_string1) { ... }
+//   MATCHER_P2(Blah, a, b, description_string2) { ... }
+//
+// Caveats
+// =======
+//
+// When defining a new matcher, you should also consider implementing
+// MatcherInterface or using MakePolymorphicMatcher().  These
+// approaches require more work than the MATCHER* macros, but also
+// give you more control on the types of the value being matched and
+// the matcher parameters, which may leads to better compiler error
+// messages when the matcher is used wrong.  They also allow
+// overloading matchers based on parameter types (as opposed to just
+// based on the number of parameters).
+//
+// MATCHER*() can only be used in a namespace scope as templates cannot be
+// declared inside of a local class.
+//
+// More Information
+// ================
+//
+// To learn more about using these macros, please search for 'MATCHER'
+// on
+// https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md
+//
+// This file also implements some commonly used argument matchers.  More
+// matchers can be defined by the user implementing the
+// MatcherInterface<T> interface if necessary.
+//
+// See googletest/include/gtest/gtest-matchers.h for the definition of class
+// Matcher, class MatcherInterface, and others.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+
+#include <algorithm>
+#include <cmath>
+#include <initializer_list>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gmock/internal/gmock-pp.h"
+#include "gtest/gtest.h"
+
+// MSVC warning C5046 is new as of VS2017 version 15.8.
+#if defined(_MSC_VER) && _MSC_VER >= 1915
+#define GMOCK_MAYBE_5046_ 5046
+#else
+#define GMOCK_MAYBE_5046_
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(
+    4251 GMOCK_MAYBE_5046_ /* class A needs to have dll-interface to be used by
+                              clients of class B */
+    /* Symbol involving type with internal linkage not defined */)
+
+namespace testing {
+
+// To implement a matcher Foo for type T, define:
+//   1. a class FooMatcherImpl that implements the
+//      MatcherInterface<T> interface, and
+//   2. a factory function that creates a Matcher<T> object from a
+//      FooMatcherImpl*.
+//
+// The two-level delegation design makes it possible to allow a user
+// to write "v" instead of "Eq(v)" where a Matcher is expected, which
+// is impossible if we pass matchers by pointers.  It also eases
+// ownership management as Matcher objects can now be copied like
+// plain values.
+
+// A match result listener that stores the explanation in a string.
+class StringMatchResultListener : public MatchResultListener {
+ public:
+  StringMatchResultListener() : MatchResultListener(&ss_) {}
+
+  // Returns the explanation accumulated so far.
+  std::string str() const { return ss_.str(); }
+
+  // Clears the explanation accumulated so far.
+  void Clear() { ss_.str(""); }
+
+ private:
+  ::std::stringstream ss_;
+
+  StringMatchResultListener(const StringMatchResultListener&) = delete;
+  StringMatchResultListener& operator=(const StringMatchResultListener&) =
+      delete;
+};
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// The MatcherCastImpl class template is a helper for implementing
+// MatcherCast().  We need this helper in order to partially
+// specialize the implementation of MatcherCast() (C++ allows
+// class/struct templates to be partially specialized, but not
+// function templates.).
+
+// This general version is used when MatcherCast()'s argument is a
+// polymorphic matcher (i.e. something that can be converted to a
+// Matcher but is not one yet; for example, Eq(value)) or a value (for
+// example, "hello").
+template <typename T, typename M>
+class MatcherCastImpl {
+ public:
+  static Matcher<T> Cast(const M& polymorphic_matcher_or_value) {
+    // M can be a polymorphic matcher, in which case we want to use
+    // its conversion operator to create Matcher<T>.  Or it can be a value
+    // that should be passed to the Matcher<T>'s constructor.
+    //
+    // We can't call Matcher<T>(polymorphic_matcher_or_value) when M is a
+    // polymorphic matcher because it'll be ambiguous if T has an implicit
+    // constructor from M (this usually happens when T has an implicit
+    // constructor from any type).
+    //
+    // It won't work to unconditionally implicit_cast
+    // polymorphic_matcher_or_value to Matcher<T> because it won't trigger
+    // a user-defined conversion from M to T if one exists (assuming M is
+    // a value).
+    return CastImpl(polymorphic_matcher_or_value,
+                    std::is_convertible<M, Matcher<T>>{},
+                    std::is_convertible<M, T>{});
+  }
+
+ private:
+  template <bool Ignore>
+  static Matcher<T> CastImpl(const M& polymorphic_matcher_or_value,
+                             std::true_type /* convertible_to_matcher */,
+                             std::integral_constant<bool, Ignore>) {
+    // M is implicitly convertible to Matcher<T>, which means that either
+    // M is a polymorphic matcher or Matcher<T> has an implicit constructor
+    // from M.  In both cases using the implicit conversion will produce a
+    // matcher.
+    //
+    // Even if T has an implicit constructor from M, it won't be called because
+    // creating Matcher<T> would require a chain of two user-defined conversions
+    // (first to create T from M and then to create Matcher<T> from T).
+    return polymorphic_matcher_or_value;
+  }
+
+  // M can't be implicitly converted to Matcher<T>, so M isn't a polymorphic
+  // matcher. It's a value of a type implicitly convertible to T. Use direct
+  // initialization to create a matcher.
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::true_type /* convertible_to_T */) {
+    return Matcher<T>(ImplicitCast_<T>(value));
+  }
+
+  // M can't be implicitly converted to either Matcher<T> or T. Attempt to use
+  // polymorphic matcher Eq(value) in this case.
+  //
+  // Note that we first attempt to perform an implicit cast on the value and
+  // only fall back to the polymorphic Eq() matcher afterwards because the
+  // latter calls bool operator==(const Lhs& lhs, const Rhs& rhs) in the end
+  // which might be undefined even when Rhs is implicitly convertible to Lhs
+  // (e.g. std::pair<const int, int> vs. std::pair<int, int>).
+  //
+  // We don't define this method inline as we need the declaration of Eq().
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::false_type /* convertible_to_T */);
+};
+
+// This more specialized version is used when MatcherCast()'s argument
+// is already a Matcher.  This only compiles when type T can be
+// statically converted to type U.
+template <typename T, typename U>
+class MatcherCastImpl<T, Matcher<U>> {
+ public:
+  static Matcher<T> Cast(const Matcher<U>& source_matcher) {
+    return Matcher<T>(new Impl(source_matcher));
+  }
+
+ private:
+  class Impl : public MatcherInterface<T> {
+   public:
+    explicit Impl(const Matcher<U>& source_matcher)
+        : source_matcher_(source_matcher) {}
+
+    // We delegate the matching logic to the source matcher.
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      using FromType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<T>::type>::type>::type;
+      using ToType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<U>::type>::type>::type;
+      // Do not allow implicitly converting base*/& to derived*/&.
+      static_assert(
+          // Do not trigger if only one of them is a pointer. That implies a
+          // regular conversion and not a down_cast.
+          (std::is_pointer<typename std::remove_reference<T>::type>::value !=
+           std::is_pointer<typename std::remove_reference<U>::type>::value) ||
+              std::is_same<FromType, ToType>::value ||
+              !std::is_base_of<FromType, ToType>::value,
+          "Can't implicitly convert from <base> to <derived>");
+
+      // Do the cast to `U` explicitly if necessary.
+      // Otherwise, let implicit conversions do the trick.
+      using CastType =
+          typename std::conditional<std::is_convertible<T&, const U&>::value,
+                                    T&, U>::type;
+
+      return source_matcher_.MatchAndExplain(static_cast<CastType>(x),
+                                             listener);
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      source_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      source_matcher_.DescribeNegationTo(os);
+    }
+
+   private:
+    const Matcher<U> source_matcher_;
+  };
+};
+
+// This even more specialized version is used for efficiently casting
+// a matcher to its own type.
+template <typename T>
+class MatcherCastImpl<T, Matcher<T>> {
+ public:
+  static Matcher<T> Cast(const Matcher<T>& matcher) { return matcher; }
+};
+
+// Template specialization for parameterless Matcher.
+template <typename Derived>
+class MatcherBaseImpl {
+ public:
+  MatcherBaseImpl() = default;
+
+  template <typename T>
+  operator ::testing::Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return ::testing::Matcher<T>(new
+                                 typename Derived::template gmock_Impl<T>());
+  }
+};
+
+// Template specialization for Matcher with parameters.
+template <template <typename...> class Derived, typename... Ts>
+class MatcherBaseImpl<Derived<Ts...>> {
+ public:
+  // Mark the constructor explicit for single argument T to avoid implicit
+  // conversions.
+  template <typename E = std::enable_if<sizeof...(Ts) == 1>,
+            typename E::type* = nullptr>
+  explicit MatcherBaseImpl(Ts... params)
+      : params_(std::forward<Ts>(params)...) {}
+  template <typename E = std::enable_if<sizeof...(Ts) != 1>,
+            typename = typename E::type>
+  MatcherBaseImpl(Ts... params)  // NOLINT
+      : params_(std::forward<Ts>(params)...) {}
+
+  template <typename F>
+  operator ::testing::Matcher<F>() const {  // NOLINT(runtime/explicit)
+    return Apply<F>(MakeIndexSequence<sizeof...(Ts)>{});
+  }
+
+ private:
+  template <typename F, std::size_t... tuple_ids>
+  ::testing::Matcher<F> Apply(IndexSequence<tuple_ids...>) const {
+    return ::testing::Matcher<F>(
+        new typename Derived<Ts...>::template gmock_Impl<F>(
+            std::get<tuple_ids>(params_)...));
+  }
+
+  const std::tuple<Ts...> params_;
+};
+
+}  // namespace internal
+
+// In order to be safe and clear, casting between different matcher
+// types is done explicitly via MatcherCast<T>(m), which takes a
+// matcher m and returns a Matcher<T>.  It compiles only when T can be
+// statically converted to the argument type of m.
+template <typename T, typename M>
+inline Matcher<T> MatcherCast(const M& matcher) {
+  return internal::MatcherCastImpl<T, M>::Cast(matcher);
+}
+
+// This overload handles polymorphic matchers and values only since
+// monomorphic matchers are handled by the next one.
+template <typename T, typename M>
+inline Matcher<T> SafeMatcherCast(const M& polymorphic_matcher_or_value) {
+  return MatcherCast<T>(polymorphic_matcher_or_value);
+}
+
+// This overload handles monomorphic matchers.
+//
+// In general, if type T can be implicitly converted to type U, we can
+// safely convert a Matcher<U> to a Matcher<T> (i.e. Matcher is
+// contravariant): just keep a copy of the original Matcher<U>, convert the
+// argument from type T to U, and then pass it to the underlying Matcher<U>.
+// The only exception is when U is a reference and T is not, as the
+// underlying Matcher<U> may be interested in the argument's address, which
+// is not preserved in the conversion from T to U.
+template <typename T, typename U>
+inline Matcher<T> SafeMatcherCast(const Matcher<U>& matcher) {
+  // Enforce that T can be implicitly converted to U.
+  static_assert(std::is_convertible<const T&, const U&>::value,
+                "T must be implicitly convertible to U");
+  // Enforce that we are not converting a non-reference type T to a reference
+  // type U.
+  static_assert(std::is_reference<T>::value || !std::is_reference<U>::value,
+                "cannot convert non reference arg to reference");
+  // In case both T and U are arithmetic types, enforce that the
+  // conversion is not lossy.
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(T) RawT;
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(U) RawU;
+  constexpr bool kTIsOther = GMOCK_KIND_OF_(RawT) == internal::kOther;
+  constexpr bool kUIsOther = GMOCK_KIND_OF_(RawU) == internal::kOther;
+  static_assert(
+      kTIsOther || kUIsOther ||
+          (internal::LosslessArithmeticConvertible<RawT, RawU>::value),
+      "conversion of arithmetic types must be lossless");
+  return MatcherCast<T>(matcher);
+}
+
+// A<T>() returns a matcher that matches any value of type T.
+template <typename T>
+Matcher<T> A();
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// If the explanation is not empty, prints it to the ostream.
+inline void PrintIfNotEmpty(const std::string& explanation,
+                            ::std::ostream* os) {
+  if (explanation != "" && os != nullptr) {
+    *os << ", " << explanation;
+  }
+}
+
+// Returns true if the given type name is easy to read by a human.
+// This is used to decide whether printing the type of a value might
+// be helpful.
+inline bool IsReadableTypeName(const std::string& type_name) {
+  // We consider a type name readable if it's short or doesn't contain
+  // a template or function type.
+  return (type_name.length() <= 20 ||
+          type_name.find_first_of("<(") == std::string::npos);
+}
+
+// Matches the value against the given matcher, prints the value and explains
+// the match result to the listener. Returns the match result.
+// 'listener' must not be NULL.
+// Value cannot be passed by const reference, because some matchers take a
+// non-const argument.
+template <typename Value, typename T>
+bool MatchPrintAndExplain(Value& value, const Matcher<T>& matcher,
+                          MatchResultListener* listener) {
+  if (!listener->IsInterested()) {
+    // If the listener is not interested, we do not need to construct the
+    // inner explanation.
+    return matcher.Matches(value);
+  }
+
+  StringMatchResultListener inner_listener;
+  const bool match = matcher.MatchAndExplain(value, &inner_listener);
+
+  UniversalPrint(value, listener->stream());
+#if GTEST_HAS_RTTI
+  const std::string& type_name = GetTypeName<Value>();
+  if (IsReadableTypeName(type_name))
+    *listener->stream() << " (of type " << type_name << ")";
+#endif
+  PrintIfNotEmpty(inner_listener.str(), listener->stream());
+
+  return match;
+}
+
+// An internal helper class for doing compile-time loop on a tuple's
+// fields.
+template <size_t N>
+class TuplePrefix {
+ public:
+  // TuplePrefix<N>::Matches(matcher_tuple, value_tuple) returns true
+  // if and only if the first N fields of matcher_tuple matches
+  // the first N fields of value_tuple, respectively.
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& matcher_tuple,
+                      const ValueTuple& value_tuple) {
+    return TuplePrefix<N - 1>::Matches(matcher_tuple, value_tuple) &&
+           std::get<N - 1>(matcher_tuple).Matches(std::get<N - 1>(value_tuple));
+  }
+
+  // TuplePrefix<N>::ExplainMatchFailuresTo(matchers, values, os)
+  // describes failures in matching the first N fields of matchers
+  // against the first N fields of values.  If there is no failure,
+  // nothing will be streamed to os.
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& matchers,
+                                     const ValueTuple& values,
+                                     ::std::ostream* os) {
+    // First, describes failures in the first N - 1 fields.
+    TuplePrefix<N - 1>::ExplainMatchFailuresTo(matchers, values, os);
+
+    // Then describes the failure (if any) in the (N - 1)-th (0-based)
+    // field.
+    typename std::tuple_element<N - 1, MatcherTuple>::type matcher =
+        std::get<N - 1>(matchers);
+    typedef typename std::tuple_element<N - 1, ValueTuple>::type Value;
+    const Value& value = std::get<N - 1>(values);
+    StringMatchResultListener listener;
+    if (!matcher.MatchAndExplain(value, &listener)) {
+      *os << "  Expected arg #" << N - 1 << ": ";
+      std::get<N - 1>(matchers).DescribeTo(os);
+      *os << "\n           Actual: ";
+      // We remove the reference in type Value to prevent the
+      // universal printer from printing the address of value, which
+      // isn't interesting to the user most of the time.  The
+      // matcher's MatchAndExplain() method handles the case when
+      // the address is interesting.
+      internal::UniversalPrint(value, os);
+      PrintIfNotEmpty(listener.str(), os);
+      *os << "\n";
+    }
+  }
+};
+
+// The base case.
+template <>
+class TuplePrefix<0> {
+ public:
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& /* matcher_tuple */,
+                      const ValueTuple& /* value_tuple */) {
+    return true;
+  }
+
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& /* matchers */,
+                                     const ValueTuple& /* values */,
+                                     ::std::ostream* /* os */) {}
+};
+
+// TupleMatches(matcher_tuple, value_tuple) returns true if and only if
+// all matchers in matcher_tuple match the corresponding fields in
+// value_tuple.  It is a compiler error if matcher_tuple and
+// value_tuple have different number of fields or incompatible field
+// types.
+template <typename MatcherTuple, typename ValueTuple>
+bool TupleMatches(const MatcherTuple& matcher_tuple,
+                  const ValueTuple& value_tuple) {
+  // Makes sure that matcher_tuple and value_tuple have the same
+  // number of fields.
+  static_assert(std::tuple_size<MatcherTuple>::value ==
+                    std::tuple_size<ValueTuple>::value,
+                "matcher and value have different numbers of fields");
+  return TuplePrefix<std::tuple_size<ValueTuple>::value>::Matches(matcher_tuple,
+                                                                  value_tuple);
+}
+
+// Describes failures in matching matchers against values.  If there
+// is no failure, nothing will be streamed to os.
+template <typename MatcherTuple, typename ValueTuple>
+void ExplainMatchFailureTupleTo(const MatcherTuple& matchers,
+                                const ValueTuple& values, ::std::ostream* os) {
+  TuplePrefix<std::tuple_size<MatcherTuple>::value>::ExplainMatchFailuresTo(
+      matchers, values, os);
+}
+
+// TransformTupleValues and its helper.
+//
+// TransformTupleValuesHelper hides the internal machinery that
+// TransformTupleValues uses to implement a tuple traversal.
+template <typename Tuple, typename Func, typename OutIter>
+class TransformTupleValuesHelper {
+ private:
+  typedef ::std::tuple_size<Tuple> TupleSize;
+
+ public:
+  // For each member of tuple 't', taken in order, evaluates '*out++ = f(t)'.
+  // Returns the final value of 'out' in case the caller needs it.
+  static OutIter Run(Func f, const Tuple& t, OutIter out) {
+    return IterateOverTuple<Tuple, TupleSize::value>()(f, t, out);
+  }
+
+ private:
+  template <typename Tup, size_t kRemainingSize>
+  struct IterateOverTuple {
+    OutIter operator()(Func f, const Tup& t, OutIter out) const {
+      *out++ = f(::std::get<TupleSize::value - kRemainingSize>(t));
+      return IterateOverTuple<Tup, kRemainingSize - 1>()(f, t, out);
+    }
+  };
+  template <typename Tup>
+  struct IterateOverTuple<Tup, 0> {
+    OutIter operator()(Func /* f */, const Tup& /* t */, OutIter out) const {
+      return out;
+    }
+  };
+};
+
+// Successively invokes 'f(element)' on each element of the tuple 't',
+// appending each result to the 'out' iterator. Returns the final value
+// of 'out'.
+template <typename Tuple, typename Func, typename OutIter>
+OutIter TransformTupleValues(Func f, const Tuple& t, OutIter out) {
+  return TransformTupleValuesHelper<Tuple, Func, OutIter>::Run(f, t, out);
+}
+
+// Implements _, a matcher that matches any value of any
+// type.  This is a polymorphic matcher, so we need a template type
+// conversion operator to make it appearing as a Matcher<T> for any
+// type T.
+class AnythingMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  template <typename T>
+  bool MatchAndExplain(const T& /* x */, std::ostream* /* listener */) const {
+    return true;
+  }
+  void DescribeTo(std::ostream* os) const { *os << "is anything"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    // This is mostly for completeness' sake, as it's not very useful
+    // to write Not(A<bool>()).  However we cannot completely rule out
+    // such a possibility, and it doesn't hurt to be prepared.
+    *os << "never matches";
+  }
+};
+
+// Implements the polymorphic IsNull() matcher, which matches any raw or smart
+// pointer that is NULL.
+class IsNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p == nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "isn't NULL"; }
+};
+
+// Implements the polymorphic NotNull() matcher, which matches any raw or smart
+// pointer that is not NULL.
+class NotNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p != nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "isn't NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "is NULL"; }
+};
+
+// Ref(variable) matches any argument that is a reference to
+// 'variable'.  This matcher is polymorphic as it can match any
+// super type of the type of 'variable'.
+//
+// The RefMatcher template class implements Ref(variable).  It can
+// only be instantiated with a reference type.  This prevents a user
+// from mistakenly using Ref(x) to match a non-reference function
+// argument.  For example, the following will righteously cause a
+// compiler error:
+//
+//   int n;
+//   Matcher<int> m1 = Ref(n);   // This won't compile.
+//   Matcher<int&> m2 = Ref(n);  // This will compile.
+template <typename T>
+class RefMatcher;
+
+template <typename T>
+class RefMatcher<T&> {
+  // Google Mock is a generic framework and thus needs to support
+  // mocking any function types, including those that take non-const
+  // reference arguments.  Therefore the template parameter T (and
+  // Super below) can be instantiated to either a const type or a
+  // non-const type.
+ public:
+  // RefMatcher() takes a T& instead of const T&, as we want the
+  // compiler to catch using Ref(const_value) as a matcher for a
+  // non-const reference.
+  explicit RefMatcher(T& x) : object_(x) {}  // NOLINT
+
+  template <typename Super>
+  operator Matcher<Super&>() const {
+    // By passing object_ (type T&) to Impl(), which expects a Super&,
+    // we make sure that Super is a super type of T.  In particular,
+    // this catches using Ref(const_value) as a matcher for a
+    // non-const reference, as you cannot implicitly convert a const
+    // reference to a non-const reference.
+    return MakeMatcher(new Impl<Super>(object_));
+  }
+
+ private:
+  template <typename Super>
+  class Impl : public MatcherInterface<Super&> {
+   public:
+    explicit Impl(Super& x) : object_(x) {}  // NOLINT
+
+    // MatchAndExplain() takes a Super& (as opposed to const Super&)
+    // in order to match the interface MatcherInterface<Super&>.
+    bool MatchAndExplain(Super& x,
+                         MatchResultListener* listener) const override {
+      *listener << "which is located @" << static_cast<const void*>(&x);
+      return &x == &object_;
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "references the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not reference the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+   private:
+    const Super& object_;
+  };
+
+  T& object_;
+};
+
+// Polymorphic helper functions for narrow and wide string matchers.
+inline bool CaseInsensitiveCStringEquals(const char* lhs, const char* rhs) {
+  return String::CaseInsensitiveCStringEquals(lhs, rhs);
+}
+
+inline bool CaseInsensitiveCStringEquals(const wchar_t* lhs,
+                                         const wchar_t* rhs) {
+  return String::CaseInsensitiveWideCStringEquals(lhs, rhs);
+}
+
+// String comparison for narrow or wide strings that can have embedded NUL
+// characters.
+template <typename StringType>
+bool CaseInsensitiveStringEquals(const StringType& s1, const StringType& s2) {
+  // Are the heads equal?
+  if (!CaseInsensitiveCStringEquals(s1.c_str(), s2.c_str())) {
+    return false;
+  }
+
+  // Skip the equal heads.
+  const typename StringType::value_type nul = 0;
+  const size_t i1 = s1.find(nul), i2 = s2.find(nul);
+
+  // Are we at the end of either s1 or s2?
+  if (i1 == StringType::npos || i2 == StringType::npos) {
+    return i1 == i2;
+  }
+
+  // Are the tails equal?
+  return CaseInsensitiveStringEquals(s1.substr(i1 + 1), s2.substr(i2 + 1));
+}
+
+// String matchers.
+
+// Implements equality-based string matchers like StrEq, StrCaseNe, and etc.
+template <typename StringType>
+class StrEqualityMatcher {
+ public:
+  StrEqualityMatcher(StringType str, bool expect_eq, bool case_sensitive)
+      : string_(std::move(str)),
+        expect_eq_(expect_eq),
+        case_sensitive_(case_sensitive) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    if (s == nullptr) {
+      return !expect_eq_;
+    }
+    return MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType s2(s);
+    const bool eq = case_sensitive_ ? s2 == string_
+                                    : CaseInsensitiveStringEquals(s2, string_);
+    return expect_eq_ == eq;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    DescribeToHelper(expect_eq_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    DescribeToHelper(!expect_eq_, os);
+  }
+
+ private:
+  void DescribeToHelper(bool expect_eq, ::std::ostream* os) const {
+    *os << (expect_eq ? "is " : "isn't ");
+    *os << "equal to ";
+    if (!case_sensitive_) {
+      *os << "(ignoring case) ";
+    }
+    UniversalPrint(string_, os);
+  }
+
+  const StringType string_;
+  const bool expect_eq_;
+  const bool case_sensitive_;
+};
+
+// Implements the polymorphic HasSubstr(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class HasSubstrMatcher {
+ public:
+  explicit HasSubstrMatcher(const StringType& substring)
+      : substring_(substring) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    return StringType(s).find(substring_) != StringType::npos;
+  }
+
+  // Describes what this matcher matches.
+  void DescribeTo(::std::ostream* os) const {
+    *os << "has substring ";
+    UniversalPrint(substring_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "has no substring ";
+    UniversalPrint(substring_, os);
+  }
+
+ private:
+  const StringType substring_;
+};
+
+// Implements the polymorphic StartsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class StartsWithMatcher {
+ public:
+  explicit StartsWithMatcher(const StringType& prefix) : prefix_(prefix) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= prefix_.length() &&
+           s2.substr(0, prefix_.length()) == prefix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "starts with ";
+    UniversalPrint(prefix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't start with ";
+    UniversalPrint(prefix_, os);
+  }
+
+ private:
+  const StringType prefix_;
+};
+
+// Implements the polymorphic EndsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class EndsWithMatcher {
+ public:
+  explicit EndsWithMatcher(const StringType& suffix) : suffix_(suffix) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= suffix_.length() &&
+           s2.substr(s2.length() - suffix_.length()) == suffix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "ends with ";
+    UniversalPrint(suffix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't end with ";
+    UniversalPrint(suffix_, os);
+  }
+
+ private:
+  const StringType suffix_;
+};
+
+// Implements the polymorphic WhenBase64Unescaped(matcher) matcher, which can be
+// used as a Matcher<T> as long as T can be converted to a string.
+class WhenBase64UnescapedMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  explicit WhenBase64UnescapedMatcher(
+      const Matcher<const std::string&>& internal_matcher)
+      : internal_matcher_(internal_matcher) {}
+
+  // Matches anything that can convert to std::string.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* listener) const {
+    const std::string s2(s);  // NOLINT (needed for working with string_view).
+    std::string unescaped;
+    if (!internal::Base64Unescape(s2, &unescaped)) {
+      if (listener != nullptr) {
+        *listener << "is not a valid base64 escaped string";
+      }
+      return false;
+    }
+    return MatchPrintAndExplain(unescaped, internal_matcher_, listener);
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "matches after Base64Unescape ";
+    internal_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "does not match after Base64Unescape ";
+    internal_matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<const std::string&> internal_matcher_;
+};
+
+// Implements a matcher that compares the two fields of a 2-tuple
+// using one of the ==, <=, <, etc, operators.  The two fields being
+// compared don't have to have the same type.
+//
+// The matcher defined here is polymorphic (for example, Eq() can be
+// used to match a std::tuple<int, short>, a std::tuple<const long&, double>,
+// etc).  Therefore we use a template type conversion operator in the
+// implementation.
+template <typename D, typename Op>
+class PairMatchBase {
+ public:
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return Matcher<::std::tuple<T1, T2>>(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << D::Desc();
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* /* listener */) const override {
+      return Op()(::std::get<0>(args), ::std::get<1>(args));
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+  };
+};
+
+class Eq2Matcher : public PairMatchBase<Eq2Matcher, AnyEq> {
+ public:
+  static const char* Desc() { return "an equal pair"; }
+};
+class Ne2Matcher : public PairMatchBase<Ne2Matcher, AnyNe> {
+ public:
+  static const char* Desc() { return "an unequal pair"; }
+};
+class Lt2Matcher : public PairMatchBase<Lt2Matcher, AnyLt> {
+ public:
+  static const char* Desc() { return "a pair where the first < the second"; }
+};
+class Gt2Matcher : public PairMatchBase<Gt2Matcher, AnyGt> {
+ public:
+  static const char* Desc() { return "a pair where the first > the second"; }
+};
+class Le2Matcher : public PairMatchBase<Le2Matcher, AnyLe> {
+ public:
+  static const char* Desc() { return "a pair where the first <= the second"; }
+};
+class Ge2Matcher : public PairMatchBase<Ge2Matcher, AnyGe> {
+ public:
+  static const char* Desc() { return "a pair where the first >= the second"; }
+};
+
+// Implements the Not(...) matcher for a particular argument type T.
+// We do not nest it inside the NotMatcher class template, as that
+// will prevent different instantiations of NotMatcher from sharing
+// the same NotMatcherImpl<T> class.
+template <typename T>
+class NotMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit NotMatcherImpl(const Matcher<T>& matcher) : matcher_(matcher) {}
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    return !matcher_.MatchAndExplain(x, listener);
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    matcher_.DescribeNegationTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<T> matcher_;
+};
+
+// Implements the Not(m) matcher, which matches a value that doesn't
+// match matcher m.
+template <typename InnerMatcher>
+class NotMatcher {
+ public:
+  explicit NotMatcher(InnerMatcher matcher) : matcher_(matcher) {}
+
+  // This template type conversion operator allows Not(m) to be used
+  // to match any type m can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(new NotMatcherImpl<T>(SafeMatcherCast<T>(matcher_)));
+  }
+
+ private:
+  InnerMatcher matcher_;
+};
+
+// Implements the AllOf(m1, m2) matcher for a particular argument type
+// T. We do not nest it inside the BothOfMatcher class template, as
+// that will prevent different instantiations of BothOfMatcher from
+// sharing the same BothOfMatcherImpl<T> class.
+template <typename T>
+class AllOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AllOfMatcherImpl(std::vector<Matcher<T>> matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    // If either matcher1_ or matcher2_ doesn't match x, we only need
+    // to explain why one of them fails.
+    std::string all_match_result;
+
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        if (all_match_result.empty()) {
+          all_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            all_match_result += ", and ";
+            all_match_result += result;
+          }
+        }
+      } else {
+        *listener << slistener.str();
+        return false;
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them match.
+    *listener << all_match_result;
+    return true;
+  }
+
+ private:
+  const std::vector<Matcher<T>> matchers_;
+};
+
+// VariadicMatcher is used for the variadic implementation of
+// AllOf(m_1, m_2, ...) and AnyOf(m_1, m_2, ...).
+// CombiningMatcher<T> is used to recursively combine the provided matchers
+// (of type Args...).
+template <template <typename T> class CombiningMatcher, typename... Args>
+class VariadicMatcher {
+ public:
+  VariadicMatcher(const Args&... matchers)  // NOLINT
+      : matchers_(matchers...) {
+    static_assert(sizeof...(Args) > 0, "Must have at least one matcher.");
+  }
+
+  VariadicMatcher(const VariadicMatcher&) = default;
+  VariadicMatcher& operator=(const VariadicMatcher&) = delete;
+
+  // This template type conversion operator allows an
+  // VariadicMatcher<Matcher1, Matcher2...> object to match any type that
+  // all of the provided matchers (Matcher1, Matcher2, ...) can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    std::vector<Matcher<T>> values;
+    CreateVariadicMatcher<T>(&values, std::integral_constant<size_t, 0>());
+    return Matcher<T>(new CombiningMatcher<T>(std::move(values)));
+  }
+
+ private:
+  template <typename T, size_t I>
+  void CreateVariadicMatcher(std::vector<Matcher<T>>* values,
+                             std::integral_constant<size_t, I>) const {
+    values->push_back(SafeMatcherCast<T>(std::get<I>(matchers_)));
+    CreateVariadicMatcher<T>(values, std::integral_constant<size_t, I + 1>());
+  }
+
+  template <typename T>
+  void CreateVariadicMatcher(
+      std::vector<Matcher<T>>*,
+      std::integral_constant<size_t, sizeof...(Args)>) const {}
+
+  std::tuple<Args...> matchers_;
+};
+
+template <typename... Args>
+using AllOfMatcher = VariadicMatcher<AllOfMatcherImpl, Args...>;
+
+// Implements the AnyOf(m1, m2) matcher for a particular argument type
+// T.  We do not nest it inside the AnyOfMatcher class template, as
+// that will prevent different instantiations of AnyOfMatcher from
+// sharing the same EitherOfMatcherImpl<T> class.
+template <typename T>
+class AnyOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AnyOfMatcherImpl(std::vector<Matcher<T>> matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    std::string no_match_result;
+
+    // If either matcher1_ or matcher2_ matches x, we just need to
+    // explain why *one* of them matches.
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        *listener << slistener.str();
+        return true;
+      } else {
+        if (no_match_result.empty()) {
+          no_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            no_match_result += ", and ";
+            no_match_result += result;
+          }
+        }
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them fail.
+    *listener << no_match_result;
+    return false;
+  }
+
+ private:
+  const std::vector<Matcher<T>> matchers_;
+};
+
+// AnyOfMatcher is used for the variadic implementation of AnyOf(m_1, m_2, ...).
+template <typename... Args>
+using AnyOfMatcher = VariadicMatcher<AnyOfMatcherImpl, Args...>;
+
+// ConditionalMatcher is the implementation of Conditional(cond, m1, m2)
+template <typename MatcherTrue, typename MatcherFalse>
+class ConditionalMatcher {
+ public:
+  ConditionalMatcher(bool condition, MatcherTrue matcher_true,
+                     MatcherFalse matcher_false)
+      : condition_(condition),
+        matcher_true_(std::move(matcher_true)),
+        matcher_false_(std::move(matcher_false)) {}
+
+  template <typename T>
+  operator Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return condition_ ? SafeMatcherCast<T>(matcher_true_)
+                      : SafeMatcherCast<T>(matcher_false_);
+  }
+
+ private:
+  bool condition_;
+  MatcherTrue matcher_true_;
+  MatcherFalse matcher_false_;
+};
+
+// Wrapper for implementation of Any/AllOfArray().
+template <template <class> class MatcherImpl, typename T>
+class SomeOfArrayMatcher {
+ public:
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename Iter>
+  SomeOfArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename U>
+  operator Matcher<U>() const {  // NOLINT
+    using RawU = typename std::decay<U>::type;
+    std::vector<Matcher<RawU>> matchers;
+    for (const auto& matcher : matchers_) {
+      matchers.push_back(MatcherCast<RawU>(matcher));
+    }
+    return Matcher<U>(new MatcherImpl<RawU>(std::move(matchers)));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+template <typename T>
+using AllOfArrayMatcher = SomeOfArrayMatcher<AllOfMatcherImpl, T>;
+
+template <typename T>
+using AnyOfArrayMatcher = SomeOfArrayMatcher<AnyOfMatcherImpl, T>;
+
+// Used for implementing Truly(pred), which turns a predicate into a
+// matcher.
+template <typename Predicate>
+class TrulyMatcher {
+ public:
+  explicit TrulyMatcher(Predicate pred) : predicate_(pred) {}
+
+  // This method template allows Truly(pred) to be used as a matcher
+  // for type T where T is the argument type of predicate 'pred'.  The
+  // argument is passed by reference as the predicate may be
+  // interested in the address of the argument.
+  template <typename T>
+  bool MatchAndExplain(T& x,  // NOLINT
+                       MatchResultListener* listener) const {
+    // Without the if-statement, MSVC sometimes warns about converting
+    // a value to bool (warning 4800).
+    //
+    // We cannot write 'return !!predicate_(x);' as that doesn't work
+    // when predicate_(x) returns a class convertible to bool but
+    // having no operator!().
+    if (predicate_(x)) return true;
+    *listener << "didn't satisfy the given predicate";
+    return false;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "satisfies the given predicate";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't satisfy the given predicate";
+  }
+
+ private:
+  Predicate predicate_;
+};
+
+// Used for implementing Matches(matcher), which turns a matcher into
+// a predicate.
+template <typename M>
+class MatcherAsPredicate {
+ public:
+  explicit MatcherAsPredicate(M matcher) : matcher_(matcher) {}
+
+  // This template operator() allows Matches(m) to be used as a
+  // predicate on type T where m is a matcher on type T.
+  //
+  // The argument x is passed by reference instead of by value, as
+  // some matcher may be interested in its address (e.g. as in
+  // Matches(Ref(n))(x)).
+  template <typename T>
+  bool operator()(const T& x) const {
+    // We let matcher_ commit to a particular type here instead of
+    // when the MatcherAsPredicate object was constructed.  This
+    // allows us to write Matches(m) where m is a polymorphic matcher
+    // (e.g. Eq(5)).
+    //
+    // If we write Matcher<T>(matcher_).Matches(x) here, it won't
+    // compile when matcher_ has type Matcher<const T&>; if we write
+    // Matcher<const T&>(matcher_).Matches(x) here, it won't compile
+    // when matcher_ has type Matcher<T>; if we just write
+    // matcher_.Matches(x), it won't compile when matcher_ is
+    // polymorphic, e.g. Eq(5).
+    //
+    // MatcherCast<const T&>() is necessary for making the code work
+    // in all of the above situations.
+    return MatcherCast<const T&>(matcher_).Matches(x);
+  }
+
+ private:
+  M matcher_;
+};
+
+// For implementing ASSERT_THAT() and EXPECT_THAT().  The template
+// argument M must be a type that can be converted to a matcher.
+template <typename M>
+class PredicateFormatterFromMatcher {
+ public:
+  explicit PredicateFormatterFromMatcher(M m) : matcher_(std::move(m)) {}
+
+  // This template () operator allows a PredicateFormatterFromMatcher
+  // object to act as a predicate-formatter suitable for using with
+  // Google Test's EXPECT_PRED_FORMAT1() macro.
+  template <typename T>
+  AssertionResult operator()(const char* value_text, const T& x) const {
+    // We convert matcher_ to a Matcher<const T&> *now* instead of
+    // when the PredicateFormatterFromMatcher object was constructed,
+    // as matcher_ may be polymorphic (e.g. NotNull()) and we won't
+    // know which type to instantiate it to until we actually see the
+    // type of x here.
+    //
+    // We write SafeMatcherCast<const T&>(matcher_) instead of
+    // Matcher<const T&>(matcher_), as the latter won't compile when
+    // matcher_ has type Matcher<T> (e.g. An<int>()).
+    // We don't write MatcherCast<const T&> either, as that allows
+    // potentially unsafe downcasting of the matcher argument.
+    const Matcher<const T&> matcher = SafeMatcherCast<const T&>(matcher_);
+
+    // The expected path here is that the matcher should match (i.e. that most
+    // tests pass) so optimize for this case.
+    if (matcher.Matches(x)) {
+      return AssertionSuccess();
+    }
+
+    ::std::stringstream ss;
+    ss << "Value of: " << value_text << "\n"
+       << "Expected: ";
+    matcher.DescribeTo(&ss);
+
+    // Rerun the matcher to "PrintAndExplain" the failure.
+    StringMatchResultListener listener;
+    if (MatchPrintAndExplain(x, matcher, &listener)) {
+      ss << "\n  The matcher failed on the initial attempt; but passed when "
+            "rerun to generate the explanation.";
+    }
+    ss << "\n  Actual: " << listener.str();
+    return AssertionFailure() << ss.str();
+  }
+
+ private:
+  const M matcher_;
+};
+
+// A helper function for converting a matcher to a predicate-formatter
+// without the user needing to explicitly write the type.  This is
+// used for implementing ASSERT_THAT() and EXPECT_THAT().
+// Implementation detail: 'matcher' is received by-value to force decaying.
+template <typename M>
+inline PredicateFormatterFromMatcher<M> MakePredicateFormatterFromMatcher(
+    M matcher) {
+  return PredicateFormatterFromMatcher<M>(std::move(matcher));
+}
+
+// Implements the polymorphic IsNan() matcher, which matches any floating type
+// value that is Nan.
+class IsNanMatcher {
+ public:
+  template <typename FloatType>
+  bool MatchAndExplain(const FloatType& f,
+                       MatchResultListener* /* listener */) const {
+    return (::std::isnan)(f);
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NaN"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "isn't NaN"; }
+};
+
+// Implements the polymorphic floating point equality matcher, which matches
+// two float values using ULP-based approximation or, optionally, a
+// user-specified epsilon.  The template is meant to be instantiated with
+// FloatType being either float or double.
+template <typename FloatType>
+class FloatingEqMatcher {
+ public:
+  // Constructor for FloatingEqMatcher.
+  // The matcher's input will be compared with expected.  The matcher treats two
+  // NANs as equal if nan_eq_nan is true.  Otherwise, under IEEE standards,
+  // equality comparisons between NANs will always return false.  We specify a
+  // negative max_abs_error_ term to indicate that ULP-based approximation will
+  // be used for comparison.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan)
+      : expected_(expected), nan_eq_nan_(nan_eq_nan), max_abs_error_(-1) {}
+
+  // Constructor that supports a user-specified max_abs_error that will be used
+  // for comparison instead of ULP-based approximation.  The max absolute
+  // should be non-negative.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan,
+                    FloatType max_abs_error)
+      : expected_(expected),
+        nan_eq_nan_(nan_eq_nan),
+        max_abs_error_(max_abs_error) {
+    GTEST_CHECK_(max_abs_error >= 0)
+        << ", where max_abs_error is" << max_abs_error;
+  }
+
+  // Implements floating point equality matcher as a Matcher<T>.
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    Impl(FloatType expected, bool nan_eq_nan, FloatType max_abs_error)
+        : expected_(expected),
+          nan_eq_nan_(nan_eq_nan),
+          max_abs_error_(max_abs_error) {}
+
+    bool MatchAndExplain(T value,
+                         MatchResultListener* listener) const override {
+      const FloatingPoint<FloatType> actual(value), expected(expected_);
+
+      // Compares NaNs first, if nan_eq_nan_ is true.
+      if (actual.is_nan() || expected.is_nan()) {
+        if (actual.is_nan() && expected.is_nan()) {
+          return nan_eq_nan_;
+        }
+        // One is nan; the other is not nan.
+        return false;
+      }
+      if (HasMaxAbsError()) {
+        // We perform an equality check so that inf will match inf, regardless
+        // of error bounds.  If the result of value - expected_ would result in
+        // overflow or if either value is inf, the default result is infinity,
+        // which should only match if max_abs_error_ is also infinity.
+        if (value == expected_) {
+          return true;
+        }
+
+        const FloatType diff = value - expected_;
+        if (::std::fabs(diff) <= max_abs_error_) {
+          return true;
+        }
+
+        if (listener->IsInterested()) {
+          *listener << "which is " << diff << " from " << expected_;
+        }
+        return false;
+      } else {
+        return actual.AlmostEquals(expected);
+      }
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      // os->precision() returns the previously set precision, which we
+      // store to restore the ostream to its original configuration
+      // after outputting.
+      const ::std::streamsize old_precision =
+          os->precision(::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "is NaN";
+        } else {
+          *os << "never matches";
+        }
+      } else {
+        *os << "is approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error <= " << max_abs_error_ << ")";
+        }
+      }
+      os->precision(old_precision);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      // As before, get original precision.
+      const ::std::streamsize old_precision =
+          os->precision(::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "isn't NaN";
+        } else {
+          *os << "is anything";
+        }
+      } else {
+        *os << "isn't approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error > " << max_abs_error_ << ")";
+        }
+      }
+      // Restore original precision.
+      os->precision(old_precision);
+    }
+
+   private:
+    bool HasMaxAbsError() const { return max_abs_error_ >= 0; }
+
+    const FloatType expected_;
+    const bool nan_eq_nan_;
+    // max_abs_error will be used for value comparison when >= 0.
+    const FloatType max_abs_error_;
+  };
+
+  // The following 3 type conversion operators allow FloatEq(expected) and
+  // NanSensitiveFloatEq(expected) to be used as a Matcher<float>, a
+  // Matcher<const float&>, or a Matcher<float&>, but nothing else.
+  operator Matcher<FloatType>() const {
+    return MakeMatcher(
+        new Impl<FloatType>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<const FloatType&>() const {
+    return MakeMatcher(
+        new Impl<const FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<FloatType&>() const {
+    return MakeMatcher(
+        new Impl<FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+ private:
+  const FloatType expected_;
+  const bool nan_eq_nan_;
+  // max_abs_error will be used for value comparison when >= 0.
+  const FloatType max_abs_error_;
+};
+
+// A 2-tuple ("binary") wrapper around FloatingEqMatcher:
+// FloatingEq2Matcher() matches (x, y) by matching FloatingEqMatcher(x, false)
+// against y, and FloatingEq2Matcher(e) matches FloatingEqMatcher(x, false, e)
+// against y. The former implements "Eq", the latter "Near". At present, there
+// is no version that compares NaNs as equal.
+template <typename FloatType>
+class FloatingEq2Matcher {
+ public:
+  FloatingEq2Matcher() { Init(-1, false); }
+
+  explicit FloatingEq2Matcher(bool nan_eq_nan) { Init(-1, nan_eq_nan); }
+
+  explicit FloatingEq2Matcher(FloatType max_abs_error) {
+    Init(max_abs_error, false);
+  }
+
+  FloatingEq2Matcher(FloatType max_abs_error, bool nan_eq_nan) {
+    Init(max_abs_error, nan_eq_nan);
+  }
+
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return MakeMatcher(
+        new Impl<::std::tuple<T1, T2>>(max_abs_error_, nan_eq_nan_));
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(
+        new Impl<const ::std::tuple<T1, T2>&>(max_abs_error_, nan_eq_nan_));
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << "an almost-equal pair";
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    Impl(FloatType max_abs_error, bool nan_eq_nan)
+        : max_abs_error_(max_abs_error), nan_eq_nan_(nan_eq_nan) {}
+
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* listener) const override {
+      if (max_abs_error_ == -1) {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      } else {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_,
+                                        max_abs_error_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      }
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+
+   private:
+    FloatType max_abs_error_;
+    const bool nan_eq_nan_;
+  };
+
+  void Init(FloatType max_abs_error_val, bool nan_eq_nan_val) {
+    max_abs_error_ = max_abs_error_val;
+    nan_eq_nan_ = nan_eq_nan_val;
+  }
+  FloatType max_abs_error_;
+  bool nan_eq_nan_;
+};
+
+// Implements the Pointee(m) matcher for matching a pointer whose
+// pointee matches matcher m.  The pointer can be either raw or smart.
+template <typename InnerMatcher>
+class PointeeMatcher {
+ public:
+  explicit PointeeMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointee(m) to be
+  // used as a matcher for any pointer type whose pointee type is
+  // compatible with the inner matcher, where type Pointer can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointee().
+  template <typename Pointer>
+  operator Matcher<Pointer>() const {
+    return Matcher<Pointer>(new Impl<const Pointer&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename Pointer>
+  class Impl : public MatcherInterface<Pointer> {
+   public:
+    using Pointee =
+        typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            Pointer)>::element_type;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<const Pointee&>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "points to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not point to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Pointer pointer,
+                         MatchResultListener* listener) const override {
+      if (GetRawPointer(pointer) == nullptr) return false;
+
+      *listener << "which points to ";
+      return MatchPrintAndExplain(*pointer, matcher_, listener);
+    }
+
+   private:
+    const Matcher<const Pointee&> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+// Implements the Pointer(m) matcher
+// Implements the Pointer(m) matcher for matching a pointer that matches matcher
+// m.  The pointer can be either raw or smart, and will match `m` against the
+// raw pointer.
+template <typename InnerMatcher>
+class PointerMatcher {
+ public:
+  explicit PointerMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointer(m) to be
+  // used as a matcher for any pointer type whose pointer type is
+  // compatible with the inner matcher, where type PointerType can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointer().
+  template <typename PointerType>
+  operator Matcher<PointerType>() const {  // NOLINT
+    return Matcher<PointerType>(new Impl<const PointerType&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename PointerType>
+  class Impl : public MatcherInterface<PointerType> {
+   public:
+    using Pointer =
+        const typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            PointerType)>::element_type*;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Pointer>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "is a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "is not a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(PointerType pointer,
+                         MatchResultListener* listener) const override {
+      *listener << "which is a pointer that ";
+      Pointer p = GetRawPointer(pointer);
+      return MatchPrintAndExplain(p, matcher_, listener);
+    }
+
+   private:
+    Matcher<Pointer> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+#if GTEST_HAS_RTTI
+// Implements the WhenDynamicCastTo<T>(m) matcher that matches a pointer or
+// reference that matches inner_matcher when dynamic_cast<T> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+class WhenDynamicCastToMatcherBase {
+ public:
+  explicit WhenDynamicCastToMatcherBase(const Matcher<To>& matcher)
+      : matcher_(matcher) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeNegationTo(os);
+  }
+
+ protected:
+  const Matcher<To> matcher_;
+
+  static std::string GetToName() { return GetTypeName<To>(); }
+
+ private:
+  static void GetCastTypeDescription(::std::ostream* os) {
+    *os << "when dynamic_cast to " << GetToName() << ", ";
+  }
+};
+
+// Primary template.
+// To is a pointer. Cast and forward the result.
+template <typename To>
+class WhenDynamicCastToMatcher : public WhenDynamicCastToMatcherBase<To> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To>& matcher)
+      : WhenDynamicCastToMatcherBase<To>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From from, MatchResultListener* listener) const {
+    To to = dynamic_cast<To>(from);
+    return MatchPrintAndExplain(to, this->matcher_, listener);
+  }
+};
+
+// Specialize for references.
+// In this case we return false if the dynamic_cast fails.
+template <typename To>
+class WhenDynamicCastToMatcher<To&> : public WhenDynamicCastToMatcherBase<To&> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To&>& matcher)
+      : WhenDynamicCastToMatcherBase<To&>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From& from, MatchResultListener* listener) const {
+    // We don't want an std::bad_cast here, so do the cast with pointers.
+    To* to = dynamic_cast<To*>(&from);
+    if (to == nullptr) {
+      *listener << "which cannot be dynamic_cast to " << this->GetToName();
+      return false;
+    }
+    return MatchPrintAndExplain(*to, this->matcher_, listener);
+  }
+};
+#endif  // GTEST_HAS_RTTI
+
+// Implements the Field() matcher for matching a field (i.e. member
+// variable) of an object.
+template <typename Class, typename FieldType>
+class FieldMatcher {
+ public:
+  FieldMatcher(FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field), matcher_(matcher), whose_field_("whose given field ") {}
+
+  FieldMatcher(const std::string& field_name, FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field),
+        matcher_(matcher),
+        whose_field_("whose field `" + field_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& value, MatchResultListener* listener) const {
+    // FIXME: The dispatch on std::is_pointer was introduced as a workaround for
+    // a compiler bug, and can now be removed.
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_field_ << "is ";
+    return MatchPrintAndExplain(obj.*field_, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a field, it must be a class/struct/union type and
+    // thus cannot be a pointer.  Therefore we pass false_type() as
+    // the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  const FieldType Class::*field_;
+  const Matcher<const FieldType&> matcher_;
+
+  // Contains either "whose given field " if the name of the field is unknown
+  // or "whose field `name_of_field` " if the name is known.
+  const std::string whose_field_;
+};
+
+// Implements the Property() matcher for matching a property
+// (i.e. return value of a getter method) of an object.
+//
+// Property is a const-qualified member function of Class returning
+// PropertyType.
+template <typename Class, typename PropertyType, typename Property>
+class PropertyMatcher {
+ public:
+  typedef const PropertyType& RefToConstProperty;
+
+  PropertyMatcher(Property property, const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose given property ") {}
+
+  PropertyMatcher(const std::string& property_name, Property property,
+                  const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose property `" + property_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& value, MatchResultListener* listener) const {
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_property_ << "is ";
+    // Cannot pass the return value (for example, int) to MatchPrintAndExplain,
+    // which takes a non-const reference as argument.
+    RefToConstProperty result = (obj.*property_)();
+    return MatchPrintAndExplain(result, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a property method, it must be a class/struct/union
+    // type and thus cannot be a pointer.  Therefore we pass
+    // false_type() as the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  Property property_;
+  const Matcher<RefToConstProperty> matcher_;
+
+  // Contains either "whose given property " if the name of the property is
+  // unknown or "whose property `name_of_property` " if the name is known.
+  const std::string whose_property_;
+};
+
+// Type traits specifying various features of different functors for ResultOf.
+// The default template specifies features for functor objects.
+template <typename Functor>
+struct CallableTraits {
+  typedef Functor StorageType;
+
+  static void CheckIsValid(Functor /* functor */) {}
+
+  template <typename T>
+  static auto Invoke(Functor f, const T& arg) -> decltype(f(arg)) {
+    return f(arg);
+  }
+};
+
+// Specialization for function pointers.
+template <typename ArgType, typename ResType>
+struct CallableTraits<ResType (*)(ArgType)> {
+  typedef ResType ResultType;
+  typedef ResType (*StorageType)(ArgType);
+
+  static void CheckIsValid(ResType (*f)(ArgType)) {
+    GTEST_CHECK_(f != nullptr)
+        << "NULL function pointer is passed into ResultOf().";
+  }
+  template <typename T>
+  static ResType Invoke(ResType (*f)(ArgType), T arg) {
+    return (*f)(arg);
+  }
+};
+
+// Implements the ResultOf() matcher for matching a return value of a
+// unary function of an object.
+template <typename Callable, typename InnerMatcher>
+class ResultOfMatcher {
+ public:
+  ResultOfMatcher(Callable callable, InnerMatcher matcher)
+      : ResultOfMatcher(/*result_description=*/"", std::move(callable),
+                        std::move(matcher)) {}
+
+  ResultOfMatcher(const std::string& result_description, Callable callable,
+                  InnerMatcher matcher)
+      : result_description_(result_description),
+        callable_(std::move(callable)),
+        matcher_(std::move(matcher)) {
+    CallableTraits<Callable>::CheckIsValid(callable_);
+  }
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(
+        new Impl<const T&>(result_description_, callable_, matcher_));
+  }
+
+ private:
+  typedef typename CallableTraits<Callable>::StorageType CallableStorageType;
+
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+    using ResultType = decltype(CallableTraits<Callable>::template Invoke<T>(
+        std::declval<CallableStorageType>(), std::declval<T>()));
+
+   public:
+    template <typename M>
+    Impl(const std::string& result_description,
+         const CallableStorageType& callable, const M& matcher)
+        : result_description_(result_description),
+          callable_(callable),
+          matcher_(MatcherCast<ResultType>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      if (result_description_.empty()) {
+        *os << "is mapped by the given callable to a value that ";
+      } else {
+        *os << "whose " << result_description_ << " ";
+      }
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      if (result_description_.empty()) {
+        *os << "is mapped by the given callable to a value that ";
+      } else {
+        *os << "whose " << result_description_ << " ";
+      }
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(T obj, MatchResultListener* listener) const override {
+      if (result_description_.empty()) {
+        *listener << "which is mapped by the given callable to ";
+      } else {
+        *listener << "whose " << result_description_ << " is ";
+      }
+      // Cannot pass the return value directly to MatchPrintAndExplain, which
+      // takes a non-const reference as argument.
+      // Also, specifying template argument explicitly is needed because T could
+      // be a non-const reference (e.g. Matcher<Uncopyable&>).
+      ResultType result =
+          CallableTraits<Callable>::template Invoke<T>(callable_, obj);
+      return MatchPrintAndExplain(result, matcher_, listener);
+    }
+
+   private:
+    const std::string result_description_;
+    // Functors often define operator() as non-const method even though
+    // they are actually stateless. But we need to use them even when
+    // 'this' is a const pointer. It's the user's responsibility not to
+    // use stateful callables with ResultOf(), which doesn't guarantee
+    // how many times the callable will be invoked.
+    mutable CallableStorageType callable_;
+    const Matcher<ResultType> matcher_;
+  };  // class Impl
+
+  const std::string result_description_;
+  const CallableStorageType callable_;
+  const InnerMatcher matcher_;
+};
+
+// Implements a matcher that checks the size of an STL-style container.
+template <typename SizeMatcher>
+class SizeIsMatcher {
+ public:
+  explicit SizeIsMatcher(const SizeMatcher& size_matcher)
+      : size_matcher_(size_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(size_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    using SizeType = decltype(std::declval<Container>().size());
+    explicit Impl(const SizeMatcher& size_matcher)
+        : size_matcher_(MatcherCast<SizeType>(size_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "size ";
+      size_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "size ";
+      size_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      SizeType size = container.size();
+      StringMatchResultListener size_listener;
+      const bool result = size_matcher_.MatchAndExplain(size, &size_listener);
+      *listener << "whose size " << size
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(size_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<SizeType> size_matcher_;
+  };
+
+ private:
+  const SizeMatcher size_matcher_;
+};
+
+// Implements a matcher that checks the begin()..end() distance of an STL-style
+// container.
+template <typename DistanceMatcher>
+class BeginEndDistanceIsMatcher {
+ public:
+  explicit BeginEndDistanceIsMatcher(const DistanceMatcher& distance_matcher)
+      : distance_matcher_(distance_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(distance_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        Container)>
+        ContainerView;
+    typedef typename std::iterator_traits<
+        typename ContainerView::type::const_iterator>::difference_type
+        DistanceType;
+    explicit Impl(const DistanceMatcher& distance_matcher)
+        : distance_matcher_(MatcherCast<DistanceType>(distance_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      using std::begin;
+      using std::end;
+      DistanceType distance = std::distance(begin(container), end(container));
+      StringMatchResultListener distance_listener;
+      const bool result =
+          distance_matcher_.MatchAndExplain(distance, &distance_listener);
+      *listener << "whose distance between begin() and end() " << distance
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(distance_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<DistanceType> distance_matcher_;
+  };
+
+ private:
+  const DistanceMatcher distance_matcher_;
+};
+
+// Implements an equality matcher for any STL-style container whose elements
+// support ==. This matcher is like Eq(), but its failure explanations provide
+// more detailed information that is useful when the container is used as a set.
+// The failure message reports elements that are in one of the operands but not
+// the other. The failure messages do not report duplicate or out-of-order
+// elements in the containers (which don't properly matter to sets, but can
+// occur if the containers are vectors or lists, for example).
+//
+// Uses the container's const_iterator, value_type, operator ==,
+// begin(), and end().
+template <typename Container>
+class ContainerEqMatcher {
+ public:
+  typedef internal::StlContainerView<Container> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+
+  static_assert(!std::is_const<Container>::value,
+                "Container type must not be const");
+  static_assert(!std::is_reference<Container>::value,
+                "Container type must not be a reference");
+
+  // We make a copy of expected in case the elements in it are modified
+  // after this matcher is created.
+  explicit ContainerEqMatcher(const Container& expected)
+      : expected_(View::Copy(expected)) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "equals ";
+    UniversalPrint(expected_, os);
+  }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "does not equal ";
+    UniversalPrint(expected_, os);
+  }
+
+  template <typename LhsContainer>
+  bool MatchAndExplain(const LhsContainer& lhs,
+                       MatchResultListener* listener) const {
+    typedef internal::StlContainerView<
+        typename std::remove_const<LhsContainer>::type>
+        LhsView;
+    StlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+    if (lhs_stl_container == expected_) return true;
+
+    ::std::ostream* const os = listener->stream();
+    if (os != nullptr) {
+      // Something is different. Check for extra values first.
+      bool printed_header = false;
+      for (auto it = lhs_stl_container.begin(); it != lhs_stl_container.end();
+           ++it) {
+        if (internal::ArrayAwareFind(expected_.begin(), expected_.end(), *it) ==
+            expected_.end()) {
+          if (printed_header) {
+            *os << ", ";
+          } else {
+            *os << "which has these unexpected elements: ";
+            printed_header = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+
+      // Now check for missing values.
+      bool printed_header2 = false;
+      for (auto it = expected_.begin(); it != expected_.end(); ++it) {
+        if (internal::ArrayAwareFind(lhs_stl_container.begin(),
+                                     lhs_stl_container.end(),
+                                     *it) == lhs_stl_container.end()) {
+          if (printed_header2) {
+            *os << ", ";
+          } else {
+            *os << (printed_header ? ",\nand" : "which")
+                << " doesn't have these expected elements: ";
+            printed_header2 = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+    }
+
+    return false;
+  }
+
+ private:
+  const StlContainer expected_;
+};
+
+// A comparator functor that uses the < operator to compare two values.
+struct LessComparator {
+  template <typename T, typename U>
+  bool operator()(const T& lhs, const U& rhs) const {
+    return lhs < rhs;
+  }
+};
+
+// Implements WhenSortedBy(comparator, container_matcher).
+template <typename Comparator, typename ContainerMatcher>
+class WhenSortedByMatcher {
+ public:
+  WhenSortedByMatcher(const Comparator& comparator,
+                      const ContainerMatcher& matcher)
+      : comparator_(comparator), matcher_(matcher) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    return MakeMatcher(new Impl<LhsContainer>(comparator_, matcher_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        LhsContainer)>
+        LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    // Transforms std::pair<const Key, Value> into std::pair<Key, Value>
+    // so that we can match associative containers.
+    typedef
+        typename RemoveConstFromKey<typename LhsStlContainer::value_type>::type
+            LhsValue;
+
+    Impl(const Comparator& comparator, const ContainerMatcher& matcher)
+        : comparator_(comparator), matcher_(matcher) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      ::std::vector<LhsValue> sorted_container(lhs_stl_container.begin(),
+                                               lhs_stl_container.end());
+      ::std::sort(sorted_container.begin(), sorted_container.end(),
+                  comparator_);
+
+      if (!listener->IsInterested()) {
+        // If the listener is not interested, we do not need to
+        // construct the inner explanation.
+        return matcher_.Matches(sorted_container);
+      }
+
+      *listener << "which is ";
+      UniversalPrint(sorted_container, listener->stream());
+      *listener << " when sorted";
+
+      StringMatchResultListener inner_listener;
+      const bool match =
+          matcher_.MatchAndExplain(sorted_container, &inner_listener);
+      PrintIfNotEmpty(inner_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Comparator comparator_;
+    const Matcher<const ::std::vector<LhsValue>&> matcher_;
+
+    Impl(const Impl&) = delete;
+    Impl& operator=(const Impl&) = delete;
+  };
+
+ private:
+  const Comparator comparator_;
+  const ContainerMatcher matcher_;
+};
+
+// Implements Pointwise(tuple_matcher, rhs_container).  tuple_matcher
+// must be able to be safely cast to Matcher<std::tuple<const T1&, const
+// T2&> >, where T1 and T2 are the types of elements in the LHS
+// container and the RHS container respectively.
+template <typename TupleMatcher, typename RhsContainer>
+class PointwiseMatcher {
+  static_assert(
+      !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(RhsContainer)>::value,
+      "use UnorderedPointwise with hash tables");
+
+ public:
+  typedef internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type RhsValue;
+
+  static_assert(!std::is_const<RhsContainer>::value,
+                "RhsContainer type must not be const");
+  static_assert(!std::is_reference<RhsContainer>::value,
+                "RhsContainer type must not be a reference");
+
+  // Like ContainerEq, we make a copy of rhs in case the elements in
+  // it are modified after this matcher is created.
+  PointwiseMatcher(const TupleMatcher& tuple_matcher, const RhsContainer& rhs)
+      : tuple_matcher_(tuple_matcher), rhs_(RhsView::Copy(rhs)) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(LhsContainer)>::value,
+        "use UnorderedPointwise with hash tables");
+
+    return Matcher<LhsContainer>(
+        new Impl<const LhsContainer&>(tuple_matcher_, rhs_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        LhsContainer)>
+        LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    typedef typename LhsStlContainer::value_type LhsValue;
+    // We pass the LHS value and the RHS value to the inner matcher by
+    // reference, as they may be expensive to copy.  We must use tuple
+    // instead of pair here, as a pair cannot hold references (C++ 98,
+    // 20.2.2 [lib.pairs]).
+    typedef ::std::tuple<const LhsValue&, const RhsValue&> InnerMatcherArg;
+
+    Impl(const TupleMatcher& tuple_matcher, const RhsStlContainer& rhs)
+        // mono_tuple_matcher_ holds a monomorphic version of the tuple matcher.
+        : mono_tuple_matcher_(SafeMatcherCast<InnerMatcherArg>(tuple_matcher)),
+          rhs_(rhs) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "contains " << rhs_.size()
+          << " values, where each value and its corresponding value in ";
+      UniversalPrinter<RhsStlContainer>::Print(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "doesn't contain exactly " << rhs_.size()
+          << " values, or contains a value x at some index i"
+          << " where x and the i-th value of ";
+      UniversalPrint(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      const size_t actual_size = lhs_stl_container.size();
+      if (actual_size != rhs_.size()) {
+        *listener << "which contains " << actual_size << " values";
+        return false;
+      }
+
+      auto left = lhs_stl_container.begin();
+      auto right = rhs_.begin();
+      for (size_t i = 0; i != actual_size; ++i, ++left, ++right) {
+        if (listener->IsInterested()) {
+          StringMatchResultListener inner_listener;
+          // Create InnerMatcherArg as a temporarily object to avoid it outlives
+          // *left and *right. Dereference or the conversion to `const T&` may
+          // return temp objects, e.g. for vector<bool>.
+          if (!mono_tuple_matcher_.MatchAndExplain(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right)),
+                  &inner_listener)) {
+            *listener << "where the value pair (";
+            UniversalPrint(*left, listener->stream());
+            *listener << ", ";
+            UniversalPrint(*right, listener->stream());
+            *listener << ") at index #" << i << " don't match";
+            PrintIfNotEmpty(inner_listener.str(), listener->stream());
+            return false;
+          }
+        } else {
+          if (!mono_tuple_matcher_.Matches(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right))))
+            return false;
+        }
+      }
+
+      return true;
+    }
+
+   private:
+    const Matcher<InnerMatcherArg> mono_tuple_matcher_;
+    const RhsStlContainer rhs_;
+  };
+
+ private:
+  const TupleMatcher tuple_matcher_;
+  const RhsStlContainer rhs_;
+};
+
+// Holds the logic common to ContainsMatcherImpl and EachMatcherImpl.
+template <typename Container>
+class QuantifierMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InnerMatcher>
+  explicit QuantifierMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+            testing::SafeMatcherCast<const Element&>(inner_matcher)) {}
+
+  // Checks whether:
+  // * All elements in the container match, if all_elements_should_match.
+  // * Any element in the container matches, if !all_elements_should_match.
+  bool MatchAndExplainImpl(bool all_elements_should_match, Container container,
+                           MatchResultListener* listener) const {
+    StlContainerReference stl_container = View::ConstReference(container);
+    size_t i = 0;
+    for (auto it = stl_container.begin(); it != stl_container.end();
+         ++it, ++i) {
+      StringMatchResultListener inner_listener;
+      const bool matches = inner_matcher_.MatchAndExplain(*it, &inner_listener);
+
+      if (matches != all_elements_should_match) {
+        *listener << "whose element #" << i
+                  << (matches ? " matches" : " doesn't match");
+        PrintIfNotEmpty(inner_listener.str(), listener->stream());
+        return !all_elements_should_match;
+      }
+    }
+    return all_elements_should_match;
+  }
+
+  bool MatchAndExplainImpl(const Matcher<size_t>& count_matcher,
+                           Container container,
+                           MatchResultListener* listener) const {
+    StlContainerReference stl_container = View::ConstReference(container);
+    size_t i = 0;
+    std::vector<size_t> match_elements;
+    for (auto it = stl_container.begin(); it != stl_container.end();
+         ++it, ++i) {
+      StringMatchResultListener inner_listener;
+      const bool matches = inner_matcher_.MatchAndExplain(*it, &inner_listener);
+      if (matches) {
+        match_elements.push_back(i);
+      }
+    }
+    if (listener->IsInterested()) {
+      if (match_elements.empty()) {
+        *listener << "has no element that matches";
+      } else if (match_elements.size() == 1) {
+        *listener << "whose element #" << match_elements[0] << " matches";
+      } else {
+        *listener << "whose elements (";
+        std::string sep = "";
+        for (size_t e : match_elements) {
+          *listener << sep << e;
+          sep = ", ";
+        }
+        *listener << ") match";
+      }
+    }
+    StringMatchResultListener count_listener;
+    if (count_matcher.MatchAndExplain(match_elements.size(), &count_listener)) {
+      *listener << " and whose match quantity of " << match_elements.size()
+                << " matches";
+      PrintIfNotEmpty(count_listener.str(), listener->stream());
+      return true;
+    } else {
+      if (match_elements.empty()) {
+        *listener << " and";
+      } else {
+        *listener << " but";
+      }
+      *listener << " whose match quantity of " << match_elements.size()
+                << " does not match";
+      PrintIfNotEmpty(count_listener.str(), listener->stream());
+      return false;
+    }
+  }
+
+ protected:
+  const Matcher<const Element&> inner_matcher_;
+};
+
+// Implements Contains(element_matcher) for the given argument type Container.
+// Symmetric to EachMatcherImpl.
+template <typename Container>
+class ContainsMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit ContainsMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "contains at least one element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't contain any element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(false, container, listener);
+  }
+};
+
+// Implements Each(element_matcher) for the given argument type Container.
+// Symmetric to ContainsMatcherImpl.
+template <typename Container>
+class EachMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit EachMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "only contains elements that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "contains some element that ";
+    this->inner_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(true, container, listener);
+  }
+};
+
+// Implements Contains(element_matcher).Times(n) for the given argument type
+// Container.
+template <typename Container>
+class ContainsTimesMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit ContainsTimesMatcherImpl(InnerMatcher inner_matcher,
+                                    Matcher<size_t> count_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher),
+        count_matcher_(std::move(count_matcher)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "quantity of elements that match ";
+    this->inner_matcher_.DescribeTo(os);
+    *os << " ";
+    count_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "quantity of elements that match ";
+    this->inner_matcher_.DescribeTo(os);
+    *os << " ";
+    count_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(count_matcher_, container, listener);
+  }
+
+ private:
+  const Matcher<size_t> count_matcher_;
+};
+
+// Implements polymorphic Contains(element_matcher).Times(n).
+template <typename M>
+class ContainsTimesMatcher {
+ public:
+  explicit ContainsTimesMatcher(M m, Matcher<size_t> count_matcher)
+      : inner_matcher_(m), count_matcher_(std::move(count_matcher)) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(new ContainsTimesMatcherImpl<const Container&>(
+        inner_matcher_, count_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+  const Matcher<size_t> count_matcher_;
+};
+
+// Implements polymorphic Contains(element_matcher).
+template <typename M>
+class ContainsMatcher {
+ public:
+  explicit ContainsMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(
+        new ContainsMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+  ContainsTimesMatcher<M> Times(Matcher<size_t> count_matcher) const {
+    return ContainsTimesMatcher<M>(inner_matcher_, std::move(count_matcher));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+// Implements polymorphic Each(element_matcher).
+template <typename M>
+class EachMatcher {
+ public:
+  explicit EachMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(
+        new EachMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+struct Rank1 {};
+struct Rank0 : Rank1 {};
+
+namespace pair_getters {
+using std::get;
+template <typename T>
+auto First(T& x, Rank1) -> decltype(get<0>(x)) {  // NOLINT
+  return get<0>(x);
+}
+template <typename T>
+auto First(T& x, Rank0) -> decltype((x.first)) {  // NOLINT
+  return x.first;
+}
+
+template <typename T>
+auto Second(T& x, Rank1) -> decltype(get<1>(x)) {  // NOLINT
+  return get<1>(x);
+}
+template <typename T>
+auto Second(T& x, Rank0) -> decltype((x.second)) {  // NOLINT
+  return x.second;
+}
+}  // namespace pair_getters
+
+// Implements Key(inner_matcher) for the given argument pair type.
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename PairType>
+class KeyMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type KeyType;
+
+  template <typename InnerMatcher>
+  explicit KeyMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+            testing::SafeMatcherCast<const KeyType&>(inner_matcher)) {}
+
+  // Returns true if and only if 'key_value.first' (the key) matches the inner
+  // matcher.
+  bool MatchAndExplain(PairType key_value,
+                       MatchResultListener* listener) const override {
+    StringMatchResultListener inner_listener;
+    const bool match = inner_matcher_.MatchAndExplain(
+        pair_getters::First(key_value, Rank0()), &inner_listener);
+    const std::string explanation = inner_listener.str();
+    if (explanation != "") {
+      *listener << "whose first field is a value " << explanation;
+    }
+    return match;
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't have a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<const KeyType&> inner_matcher_;
+};
+
+// Implements polymorphic Key(matcher_for_key).
+template <typename M>
+class KeyMatcher {
+ public:
+  explicit KeyMatcher(M m) : matcher_for_key_(m) {}
+
+  template <typename PairType>
+  operator Matcher<PairType>() const {
+    return Matcher<PairType>(
+        new KeyMatcherImpl<const PairType&>(matcher_for_key_));
+  }
+
+ private:
+  const M matcher_for_key_;
+};
+
+// Implements polymorphic Address(matcher_for_address).
+template <typename InnerMatcher>
+class AddressMatcher {
+ public:
+  explicit AddressMatcher(InnerMatcher m) : matcher_(m) {}
+
+  template <typename Type>
+  operator Matcher<Type>() const {  // NOLINT
+    return Matcher<Type>(new Impl<const Type&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular object type.
+  template <typename Type>
+  class Impl : public MatcherInterface<Type> {
+   public:
+    using Address = const GTEST_REMOVE_REFERENCE_AND_CONST_(Type) *;
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Address>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "has address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not have address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Type object,
+                         MatchResultListener* listener) const override {
+      *listener << "which has address ";
+      Address address = std::addressof(object);
+      return MatchPrintAndExplain(address, matcher_, listener);
+    }
+
+   private:
+    const Matcher<Address> matcher_;
+  };
+  const InnerMatcher matcher_;
+};
+
+// Implements Pair(first_matcher, second_matcher) for the given argument pair
+// type with its two matchers. See Pair() function below.
+template <typename PairType>
+class PairMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type FirstType;
+  typedef typename RawPairType::second_type SecondType;
+
+  template <typename FirstMatcher, typename SecondMatcher>
+  PairMatcherImpl(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(
+            testing::SafeMatcherCast<const FirstType&>(first_matcher)),
+        second_matcher_(
+            testing::SafeMatcherCast<const SecondType&>(second_matcher)) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeTo(os);
+    *os << ", and has a second field that ";
+    second_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeNegationTo(os);
+    *os << ", or has a second field that ";
+    second_matcher_.DescribeNegationTo(os);
+  }
+
+  // Returns true if and only if 'a_pair.first' matches first_matcher and
+  // 'a_pair.second' matches second_matcher.
+  bool MatchAndExplain(PairType a_pair,
+                       MatchResultListener* listener) const override {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      return first_matcher_.Matches(pair_getters::First(a_pair, Rank0())) &&
+             second_matcher_.Matches(pair_getters::Second(a_pair, Rank0()));
+    }
+    StringMatchResultListener first_inner_listener;
+    if (!first_matcher_.MatchAndExplain(pair_getters::First(a_pair, Rank0()),
+                                        &first_inner_listener)) {
+      *listener << "whose first field does not match";
+      PrintIfNotEmpty(first_inner_listener.str(), listener->stream());
+      return false;
+    }
+    StringMatchResultListener second_inner_listener;
+    if (!second_matcher_.MatchAndExplain(pair_getters::Second(a_pair, Rank0()),
+                                         &second_inner_listener)) {
+      *listener << "whose second field does not match";
+      PrintIfNotEmpty(second_inner_listener.str(), listener->stream());
+      return false;
+    }
+    ExplainSuccess(first_inner_listener.str(), second_inner_listener.str(),
+                   listener);
+    return true;
+  }
+
+ private:
+  void ExplainSuccess(const std::string& first_explanation,
+                      const std::string& second_explanation,
+                      MatchResultListener* listener) const {
+    *listener << "whose both fields match";
+    if (first_explanation != "") {
+      *listener << ", where the first field is a value " << first_explanation;
+    }
+    if (second_explanation != "") {
+      *listener << ", ";
+      if (first_explanation != "") {
+        *listener << "and ";
+      } else {
+        *listener << "where ";
+      }
+      *listener << "the second field is a value " << second_explanation;
+    }
+  }
+
+  const Matcher<const FirstType&> first_matcher_;
+  const Matcher<const SecondType&> second_matcher_;
+};
+
+// Implements polymorphic Pair(first_matcher, second_matcher).
+template <typename FirstMatcher, typename SecondMatcher>
+class PairMatcher {
+ public:
+  PairMatcher(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(first_matcher), second_matcher_(second_matcher) {}
+
+  template <typename PairType>
+  operator Matcher<PairType>() const {
+    return Matcher<PairType>(
+        new PairMatcherImpl<const PairType&>(first_matcher_, second_matcher_));
+  }
+
+ private:
+  const FirstMatcher first_matcher_;
+  const SecondMatcher second_matcher_;
+};
+
+template <typename T, size_t... I>
+auto UnpackStructImpl(const T& t, IndexSequence<I...>, int)
+    -> decltype(std::tie(get<I>(t)...)) {
+  static_assert(std::tuple_size<T>::value == sizeof...(I),
+                "Number of arguments doesn't match the number of fields.");
+  return std::tie(get<I>(t)...);
+}
+
+#if defined(__cpp_structured_bindings) && __cpp_structured_bindings >= 201606
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<1>, char) {
+  const auto& [a] = t;
+  return std::tie(a);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<2>, char) {
+  const auto& [a, b] = t;
+  return std::tie(a, b);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<3>, char) {
+  const auto& [a, b, c] = t;
+  return std::tie(a, b, c);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<4>, char) {
+  const auto& [a, b, c, d] = t;
+  return std::tie(a, b, c, d);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<5>, char) {
+  const auto& [a, b, c, d, e] = t;
+  return std::tie(a, b, c, d, e);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<6>, char) {
+  const auto& [a, b, c, d, e, f] = t;
+  return std::tie(a, b, c, d, e, f);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<7>, char) {
+  const auto& [a, b, c, d, e, f, g] = t;
+  return std::tie(a, b, c, d, e, f, g);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<8>, char) {
+  const auto& [a, b, c, d, e, f, g, h] = t;
+  return std::tie(a, b, c, d, e, f, g, h);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<9>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<10>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<11>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<12>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<13>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<14>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<15>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<16>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<17>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q);
+}
+#endif  // defined(__cpp_structured_bindings)
+
+template <size_t I, typename T>
+auto UnpackStruct(const T& t)
+    -> decltype((UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0)) {
+  return (UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0);
+}
+
+// Helper function to do comma folding in C++11.
+// The array ensures left-to-right order of evaluation.
+// Usage: VariadicExpand({expr...});
+template <typename T, size_t N>
+void VariadicExpand(const T (&)[N]) {}
+
+template <typename Struct, typename StructSize>
+class FieldsAreMatcherImpl;
+
+template <typename Struct, size_t... I>
+class FieldsAreMatcherImpl<Struct, IndexSequence<I...>>
+    : public MatcherInterface<Struct> {
+  using UnpackedType =
+      decltype(UnpackStruct<sizeof...(I)>(std::declval<const Struct&>()));
+  using MatchersType = std::tuple<
+      Matcher<const typename std::tuple_element<I, UnpackedType>::type&>...>;
+
+ public:
+  template <typename Inner>
+  explicit FieldsAreMatcherImpl(const Inner& matchers)
+      : matchers_(testing::SafeMatcherCast<
+                  const typename std::tuple_element<I, UnpackedType>::type&>(
+            std::get<I>(matchers))...) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand(
+        {(*os << separator << "has field #" << I << " that ",
+          std::get<I>(matchers_).DescribeTo(os), separator = ", and ")...});
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand({(*os << separator << "has field #" << I << " that ",
+                     std::get<I>(matchers_).DescribeNegationTo(os),
+                     separator = ", or ")...});
+  }
+
+  bool MatchAndExplain(Struct t, MatchResultListener* listener) const override {
+    return MatchInternal((UnpackStruct<sizeof...(I)>)(t), listener);
+  }
+
+ private:
+  bool MatchInternal(UnpackedType tuple, MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      bool good = true;
+      VariadicExpand({good = good && std::get<I>(matchers_).Matches(
+                                         std::get<I>(tuple))...});
+      return good;
+    }
+
+    size_t failed_pos = ~size_t{};
+
+    std::vector<StringMatchResultListener> inner_listener(sizeof...(I));
+
+    VariadicExpand(
+        {failed_pos == ~size_t{} && !std::get<I>(matchers_).MatchAndExplain(
+                                        std::get<I>(tuple), &inner_listener[I])
+             ? failed_pos = I
+             : 0 ...});
+    if (failed_pos != ~size_t{}) {
+      *listener << "whose field #" << failed_pos << " does not match";
+      PrintIfNotEmpty(inner_listener[failed_pos].str(), listener->stream());
+      return false;
+    }
+
+    *listener << "whose all elements match";
+    const char* separator = ", where";
+    for (size_t index = 0; index < sizeof...(I); ++index) {
+      const std::string str = inner_listener[index].str();
+      if (!str.empty()) {
+        *listener << separator << " field #" << index << " is a value " << str;
+        separator = ", and";
+      }
+    }
+
+    return true;
+  }
+
+  MatchersType matchers_;
+};
+
+template <typename... Inner>
+class FieldsAreMatcher {
+ public:
+  explicit FieldsAreMatcher(Inner... inner) : matchers_(std::move(inner)...) {}
+
+  template <typename Struct>
+  operator Matcher<Struct>() const {  // NOLINT
+    return Matcher<Struct>(
+        new FieldsAreMatcherImpl<const Struct&, IndexSequenceFor<Inner...>>(
+            matchers_));
+  }
+
+ private:
+  std::tuple<Inner...> matchers_;
+};
+
+// Implements ElementsAre() and ElementsAreArray().
+template <typename Container>
+class ElementsAreMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename InputIter>
+  ElementsAreMatcherImpl(InputIter first, InputIter last) {
+    while (first != last) {
+      matchers_.push_back(MatcherCast<const Element&>(*first++));
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "is empty";
+    } else if (count() == 1) {
+      *os << "has 1 element that ";
+      matchers_[0].DescribeTo(os);
+    } else {
+      *os << "has " << Elements(count()) << " where\n";
+      for (size_t i = 0; i != count(); ++i) {
+        *os << "element #" << i << " ";
+        matchers_[i].DescribeTo(os);
+        if (i + 1 < count()) {
+          *os << ",\n";
+        }
+      }
+    }
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "isn't empty";
+      return;
+    }
+
+    *os << "doesn't have " << Elements(count()) << ", or\n";
+    for (size_t i = 0; i != count(); ++i) {
+      *os << "element #" << i << " ";
+      matchers_[i].DescribeNegationTo(os);
+      if (i + 1 < count()) {
+        *os << ", or\n";
+      }
+    }
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    // To work with stream-like "containers", we must only walk
+    // through the elements in one pass.
+
+    const bool listener_interested = listener->IsInterested();
+
+    // explanations[i] is the explanation of the element at index i.
+    ::std::vector<std::string> explanations(count());
+    StlContainerReference stl_container = View::ConstReference(container);
+    auto it = stl_container.begin();
+    size_t exam_pos = 0;
+    bool mismatch_found = false;  // Have we found a mismatched element yet?
+
+    // Go through the elements and matchers in pairs, until we reach
+    // the end of either the elements or the matchers, or until we find a
+    // mismatch.
+    for (; it != stl_container.end() && exam_pos != count(); ++it, ++exam_pos) {
+      bool match;  // Does the current element match the current matcher?
+      if (listener_interested) {
+        StringMatchResultListener s;
+        match = matchers_[exam_pos].MatchAndExplain(*it, &s);
+        explanations[exam_pos] = s.str();
+      } else {
+        match = matchers_[exam_pos].Matches(*it);
+      }
+
+      if (!match) {
+        mismatch_found = true;
+        break;
+      }
+    }
+    // If mismatch_found is true, 'exam_pos' is the index of the mismatch.
+
+    // Find how many elements the actual container has.  We avoid
+    // calling size() s.t. this code works for stream-like "containers"
+    // that don't define size().
+    size_t actual_count = exam_pos;
+    for (; it != stl_container.end(); ++it) {
+      ++actual_count;
+    }
+
+    if (actual_count != count()) {
+      // The element count doesn't match.  If the container is empty,
+      // there's no need to explain anything as Google Mock already
+      // prints the empty container.  Otherwise we just need to show
+      // how many elements there actually are.
+      if (listener_interested && (actual_count != 0)) {
+        *listener << "which has " << Elements(actual_count);
+      }
+      return false;
+    }
+
+    if (mismatch_found) {
+      // The element count matches, but the exam_pos-th element doesn't match.
+      if (listener_interested) {
+        *listener << "whose element #" << exam_pos << " doesn't match";
+        PrintIfNotEmpty(explanations[exam_pos], listener->stream());
+      }
+      return false;
+    }
+
+    // Every element matches its expectation.  We need to explain why
+    // (the obvious ones can be skipped).
+    if (listener_interested) {
+      bool reason_printed = false;
+      for (size_t i = 0; i != count(); ++i) {
+        const std::string& s = explanations[i];
+        if (!s.empty()) {
+          if (reason_printed) {
+            *listener << ",\nand ";
+          }
+          *listener << "whose element #" << i << " matches, " << s;
+          reason_printed = true;
+        }
+      }
+    }
+    return true;
+  }
+
+ private:
+  static Message Elements(size_t count) {
+    return Message() << count << (count == 1 ? " element" : " elements");
+  }
+
+  size_t count() const { return matchers_.size(); }
+
+  ::std::vector<Matcher<const Element&>> matchers_;
+};
+
+// Connectivity matrix of (elements X matchers), in element-major order.
+// Initially, there are no edges.
+// Use NextGraph() to iterate over all possible edge configurations.
+// Use Randomize() to generate a random edge configuration.
+class GTEST_API_ MatchMatrix {
+ public:
+  MatchMatrix(size_t num_elements, size_t num_matchers)
+      : num_elements_(num_elements),
+        num_matchers_(num_matchers),
+        matched_(num_elements_ * num_matchers_, 0) {}
+
+  size_t LhsSize() const { return num_elements_; }
+  size_t RhsSize() const { return num_matchers_; }
+  bool HasEdge(size_t ilhs, size_t irhs) const {
+    return matched_[SpaceIndex(ilhs, irhs)] == 1;
+  }
+  void SetEdge(size_t ilhs, size_t irhs, bool b) {
+    matched_[SpaceIndex(ilhs, irhs)] = b ? 1 : 0;
+  }
+
+  // Treating the connectivity matrix as a (LhsSize()*RhsSize())-bit number,
+  // adds 1 to that number; returns false if incrementing the graph left it
+  // empty.
+  bool NextGraph();
+
+  void Randomize();
+
+  std::string DebugString() const;
+
+ private:
+  size_t SpaceIndex(size_t ilhs, size_t irhs) const {
+    return ilhs * num_matchers_ + irhs;
+  }
+
+  size_t num_elements_;
+  size_t num_matchers_;
+
+  // Each element is a char interpreted as bool. They are stored as a
+  // flattened array in lhs-major order, use 'SpaceIndex()' to translate
+  // a (ilhs, irhs) matrix coordinate into an offset.
+  ::std::vector<char> matched_;
+};
+
+typedef ::std::pair<size_t, size_t> ElementMatcherPair;
+typedef ::std::vector<ElementMatcherPair> ElementMatcherPairs;
+
+// Returns a maximum bipartite matching for the specified graph 'g'.
+// The matching is represented as a vector of {element, matcher} pairs.
+GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g);
+
+struct UnorderedMatcherRequire {
+  enum Flags {
+    Superset = 1 << 0,
+    Subset = 1 << 1,
+    ExactMatch = Superset | Subset,
+  };
+};
+
+// Untyped base class for implementing UnorderedElementsAre.  By
+// putting logic that's not specific to the element type here, we
+// reduce binary bloat and increase compilation speed.
+class GTEST_API_ UnorderedElementsAreMatcherImplBase {
+ protected:
+  explicit UnorderedElementsAreMatcherImplBase(
+      UnorderedMatcherRequire::Flags matcher_flags)
+      : match_flags_(matcher_flags) {}
+
+  // A vector of matcher describers, one for each element matcher.
+  // Does not own the describers (and thus can be used only when the
+  // element matchers are alive).
+  typedef ::std::vector<const MatcherDescriberInterface*> MatcherDescriberVec;
+
+  // Describes this UnorderedElementsAre matcher.
+  void DescribeToImpl(::std::ostream* os) const;
+
+  // Describes the negation of this UnorderedElementsAre matcher.
+  void DescribeNegationToImpl(::std::ostream* os) const;
+
+  bool VerifyMatchMatrix(const ::std::vector<std::string>& element_printouts,
+                         const MatchMatrix& matrix,
+                         MatchResultListener* listener) const;
+
+  bool FindPairing(const MatchMatrix& matrix,
+                   MatchResultListener* listener) const;
+
+  MatcherDescriberVec& matcher_describers() { return matcher_describers_; }
+
+  static Message Elements(size_t n) {
+    return Message() << n << " element" << (n == 1 ? "" : "s");
+  }
+
+  UnorderedMatcherRequire::Flags match_flags() const { return match_flags_; }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  MatcherDescriberVec matcher_describers_;
+};
+
+// Implements UnorderedElementsAre, UnorderedElementsAreArray, IsSubsetOf, and
+// IsSupersetOf.
+template <typename Container>
+class UnorderedElementsAreMatcherImpl
+    : public MatcherInterface<Container>,
+      public UnorderedElementsAreMatcherImplBase {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InputIter>
+  UnorderedElementsAreMatcherImpl(UnorderedMatcherRequire::Flags matcher_flags,
+                                  InputIter first, InputIter last)
+      : UnorderedElementsAreMatcherImplBase(matcher_flags) {
+    for (; first != last; ++first) {
+      matchers_.push_back(MatcherCast<const Element&>(*first));
+    }
+    for (const auto& m : matchers_) {
+      matcher_describers().push_back(m.GetDescriber());
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeToImpl(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    StlContainerReference stl_container = View::ConstReference(container);
+    ::std::vector<std::string> element_printouts;
+    MatchMatrix matrix =
+        AnalyzeElements(stl_container.begin(), stl_container.end(),
+                        &element_printouts, listener);
+
+    if (matrix.LhsSize() == 0 && matrix.RhsSize() == 0) {
+      return true;
+    }
+
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      if (matrix.LhsSize() != matrix.RhsSize()) {
+        // The element count doesn't match.  If the container is empty,
+        // there's no need to explain anything as Google Mock already
+        // prints the empty container. Otherwise we just need to show
+        // how many elements there actually are.
+        if (matrix.LhsSize() != 0 && listener->IsInterested()) {
+          *listener << "which has " << Elements(matrix.LhsSize());
+        }
+        return false;
+      }
+    }
+
+    return VerifyMatchMatrix(element_printouts, matrix, listener) &&
+           FindPairing(matrix, listener);
+  }
+
+ private:
+  template <typename ElementIter>
+  MatchMatrix AnalyzeElements(ElementIter elem_first, ElementIter elem_last,
+                              ::std::vector<std::string>* element_printouts,
+                              MatchResultListener* listener) const {
+    element_printouts->clear();
+    ::std::vector<char> did_match;
+    size_t num_elements = 0;
+    DummyMatchResultListener dummy;
+    for (; elem_first != elem_last; ++num_elements, ++elem_first) {
+      if (listener->IsInterested()) {
+        element_printouts->push_back(PrintToString(*elem_first));
+      }
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        did_match.push_back(
+            matchers_[irhs].MatchAndExplain(*elem_first, &dummy));
+      }
+    }
+
+    MatchMatrix matrix(num_elements, matchers_.size());
+    ::std::vector<char>::const_iterator did_match_iter = did_match.begin();
+    for (size_t ilhs = 0; ilhs != num_elements; ++ilhs) {
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        matrix.SetEdge(ilhs, irhs, *did_match_iter++ != 0);
+      }
+    }
+    return matrix;
+  }
+
+  ::std::vector<Matcher<const Element&>> matchers_;
+};
+
+// Functor for use in TransformTuple.
+// Performs MatcherCast<Target> on an input argument of any type.
+template <typename Target>
+struct CastAndAppendTransform {
+  template <typename Arg>
+  Matcher<Target> operator()(const Arg& a) const {
+    return MatcherCast<Target>(a);
+  }
+};
+
+// Implements UnorderedElementsAre.
+template <typename MatcherTuple>
+class UnorderedElementsAreMatcher {
+ public:
+  explicit UnorderedElementsAreMatcher(const MatcherTuple& args)
+      : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&>> MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            UnorderedMatcherRequire::ExactMatch, matchers.begin(),
+            matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements ElementsAre.
+template <typename MatcherTuple>
+class ElementsAreMatcher {
+ public:
+  explicit ElementsAreMatcher(const MatcherTuple& args) : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value ||
+            ::std::tuple_size<MatcherTuple>::value < 2,
+        "use UnorderedElementsAre with hash tables");
+
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&>> MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers.begin(), matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements UnorderedElementsAreArray(), IsSubsetOf(), and IsSupersetOf().
+template <typename T>
+class UnorderedElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  UnorderedElementsAreArrayMatcher(UnorderedMatcherRequire::Flags match_flags,
+                                   Iter first, Iter last)
+      : match_flags_(match_flags), matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            match_flags_, matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  ::std::vector<T> matchers_;
+};
+
+// Implements ElementsAreArray().
+template <typename T>
+class ElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  ElementsAreArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value,
+        "use UnorderedElementsAreArray with hash tables");
+
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+// Given a 2-tuple matcher tm of type Tuple2Matcher and a value second
+// of type Second, BoundSecondMatcher<Tuple2Matcher, Second>(tm,
+// second) is a polymorphic matcher that matches a value x if and only if
+// tm matches tuple (x, second).  Useful for implementing
+// UnorderedPointwise() in terms of UnorderedElementsAreArray().
+//
+// BoundSecondMatcher is copyable and assignable, as we need to put
+// instances of this class in a vector when implementing
+// UnorderedPointwise().
+template <typename Tuple2Matcher, typename Second>
+class BoundSecondMatcher {
+ public:
+  BoundSecondMatcher(const Tuple2Matcher& tm, const Second& second)
+      : tuple2_matcher_(tm), second_value_(second) {}
+
+  BoundSecondMatcher(const BoundSecondMatcher& other) = default;
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return MakeMatcher(new Impl<T>(tuple2_matcher_, second_value_));
+  }
+
+  // We have to define this for UnorderedPointwise() to compile in
+  // C++98 mode, as it puts BoundSecondMatcher instances in a vector,
+  // which requires the elements to be assignable in C++98.  The
+  // compiler cannot generate the operator= for us, as Tuple2Matcher
+  // and Second may not be assignable.
+  //
+  // However, this should never be called, so the implementation just
+  // need to assert.
+  void operator=(const BoundSecondMatcher& /*rhs*/) {
+    GTEST_LOG_(FATAL) << "BoundSecondMatcher should never be assigned.";
+  }
+
+ private:
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    typedef ::std::tuple<T, Second> ArgTuple;
+
+    Impl(const Tuple2Matcher& tm, const Second& second)
+        : mono_tuple2_matcher_(SafeMatcherCast<const ArgTuple&>(tm)),
+          second_value_(second) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "and ";
+      UniversalPrint(second_value_, os);
+      *os << " ";
+      mono_tuple2_matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      return mono_tuple2_matcher_.MatchAndExplain(ArgTuple(x, second_value_),
+                                                  listener);
+    }
+
+   private:
+    const Matcher<const ArgTuple&> mono_tuple2_matcher_;
+    const Second second_value_;
+  };
+
+  const Tuple2Matcher tuple2_matcher_;
+  const Second second_value_;
+};
+
+// Given a 2-tuple matcher tm and a value second,
+// MatcherBindSecond(tm, second) returns a matcher that matches a
+// value x if and only if tm matches tuple (x, second).  Useful for
+// implementing UnorderedPointwise() in terms of UnorderedElementsAreArray().
+template <typename Tuple2Matcher, typename Second>
+BoundSecondMatcher<Tuple2Matcher, Second> MatcherBindSecond(
+    const Tuple2Matcher& tm, const Second& second) {
+  return BoundSecondMatcher<Tuple2Matcher, Second>(tm, second);
+}
+
+// Returns the description for a matcher defined using the MATCHER*()
+// macro where the user-supplied description string is "", if
+// 'negation' is false; otherwise returns the description of the
+// negation of the matcher.  'param_values' contains a list of strings
+// that are the print-out of the matcher's parameters.
+GTEST_API_ std::string FormatMatcherDescription(
+    bool negation, const char* matcher_name,
+    const std::vector<const char*>& param_names, const Strings& param_values);
+
+// Implements a matcher that checks the value of a optional<> type variable.
+template <typename ValueMatcher>
+class OptionalMatcher {
+ public:
+  explicit OptionalMatcher(const ValueMatcher& value_matcher)
+      : value_matcher_(value_matcher) {}
+
+  template <typename Optional>
+  operator Matcher<Optional>() const {
+    return Matcher<Optional>(new Impl<const Optional&>(value_matcher_));
+  }
+
+  template <typename Optional>
+  class Impl : public MatcherInterface<Optional> {
+   public:
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Optional) OptionalView;
+    typedef typename OptionalView::value_type ValueType;
+    explicit Impl(const ValueMatcher& value_matcher)
+        : value_matcher_(MatcherCast<ValueType>(value_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Optional optional,
+                         MatchResultListener* listener) const override {
+      if (!optional) {
+        *listener << "which is not engaged";
+        return false;
+      }
+      const ValueType& value = *optional;
+      StringMatchResultListener value_listener;
+      const bool match = value_matcher_.MatchAndExplain(value, &value_listener);
+      *listener << "whose value " << PrintToString(value)
+                << (match ? " matches" : " doesn't match");
+      PrintIfNotEmpty(value_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Matcher<ValueType> value_matcher_;
+  };
+
+ private:
+  const ValueMatcher value_matcher_;
+};
+
+namespace variant_matcher {
+// Overloads to allow VariantMatcher to do proper ADL lookup.
+template <typename T>
+void holds_alternative() {}
+template <typename T>
+void get() {}
+
+// Implements a matcher that checks the value of a variant<> type variable.
+template <typename T>
+class VariantMatcher {
+ public:
+  explicit VariantMatcher(::testing::Matcher<const T&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  template <typename Variant>
+  bool MatchAndExplain(const Variant& value,
+                       ::testing::MatchResultListener* listener) const {
+    using std::get;
+    if (!listener->IsInterested()) {
+      return holds_alternative<T>(value) && matcher_.Matches(get<T>(value));
+    }
+
+    if (!holds_alternative<T>(value)) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    const T& elem = get<T>(value);
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(elem, &elem_listener);
+    *listener << "whose value " << PrintToString(elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace variant_matcher
+
+namespace any_cast_matcher {
+
+// Overloads to allow AnyCastMatcher to do proper ADL lookup.
+template <typename T>
+void any_cast() {}
+
+// Implements a matcher that any_casts the value.
+template <typename T>
+class AnyCastMatcher {
+ public:
+  explicit AnyCastMatcher(const ::testing::Matcher<const T&>& matcher)
+      : matcher_(matcher) {}
+
+  template <typename AnyType>
+  bool MatchAndExplain(const AnyType& value,
+                       ::testing::MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      const T* ptr = any_cast<T>(&value);
+      return ptr != nullptr && matcher_.Matches(*ptr);
+    }
+
+    const T* elem = any_cast<T>(&value);
+    if (elem == nullptr) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(*elem, &elem_listener);
+    *listener << "whose value " << PrintToString(*elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace any_cast_matcher
+
+// Implements the Args() matcher.
+template <class ArgsTuple, size_t... k>
+class ArgsMatcherImpl : public MatcherInterface<ArgsTuple> {
+ public:
+  using RawArgsTuple = typename std::decay<ArgsTuple>::type;
+  using SelectedArgs =
+      std::tuple<typename std::tuple_element<k, RawArgsTuple>::type...>;
+  using MonomorphicInnerMatcher = Matcher<const SelectedArgs&>;
+
+  template <typename InnerMatcher>
+  explicit ArgsMatcherImpl(const InnerMatcher& inner_matcher)
+      : inner_matcher_(SafeMatcherCast<const SelectedArgs&>(inner_matcher)) {}
+
+  bool MatchAndExplain(ArgsTuple args,
+                       MatchResultListener* listener) const override {
+    // Workaround spurious C4100 on MSVC<=15.7 when k is empty.
+    (void)args;
+    const SelectedArgs& selected_args =
+        std::forward_as_tuple(std::get<k>(args)...);
+    if (!listener->IsInterested()) return inner_matcher_.Matches(selected_args);
+
+    PrintIndices(listener->stream());
+    *listener << "are " << PrintToString(selected_args);
+
+    StringMatchResultListener inner_listener;
+    const bool match =
+        inner_matcher_.MatchAndExplain(selected_args, &inner_listener);
+    PrintIfNotEmpty(inner_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  // Prints the indices of the selected fields.
+  static void PrintIndices(::std::ostream* os) {
+    *os << "whose fields (";
+    const char* sep = "";
+    // Workaround spurious C4189 on MSVC<=15.7 when k is empty.
+    (void)sep;
+    const char* dummy[] = {"", (static_cast<void>(*os << sep << "#" << k), sep = ", ")...};
+    (void)dummy;
+    *os << ") ";
+  }
+
+  MonomorphicInnerMatcher inner_matcher_;
+};
+
+template <class InnerMatcher, size_t... k>
+class ArgsMatcher {
+ public:
+  explicit ArgsMatcher(InnerMatcher inner_matcher)
+      : inner_matcher_(std::move(inner_matcher)) {}
+
+  template <typename ArgsTuple>
+  operator Matcher<ArgsTuple>() const {  // NOLINT
+    return MakeMatcher(new ArgsMatcherImpl<ArgsTuple, k...>(inner_matcher_));
+  }
+
+ private:
+  InnerMatcher inner_matcher_;
+};
+
+}  // namespace internal
+
+// ElementsAreArray(iterator_first, iterator_last)
+// ElementsAreArray(pointer, count)
+// ElementsAreArray(array)
+// ElementsAreArray(container)
+// ElementsAreArray({ e1, e2, ..., en })
+//
+// The ElementsAreArray() functions are like ElementsAre(...), except
+// that they are given a homogeneous sequence rather than taking each
+// element as a function argument. The sequence can be specified as an
+// array, a pointer and count, a vector, an initializer list, or an
+// STL iterator range. In each of these cases, the underlying sequence
+// can be either a sequence of values or a sequence of matchers.
+//
+// All forms of ElementsAreArray() make a copy of the input matcher sequence.
+
+template <typename Iter>
+inline internal::ElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+ElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::ElementsAreArrayMatcher<T>(first, last);
+}
+
+template <typename T>
+inline auto ElementsAreArray(const T* pointer, size_t count)
+    -> decltype(ElementsAreArray(pointer, pointer + count)) {
+  return ElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline auto ElementsAreArray(const T (&array)[N])
+    -> decltype(ElementsAreArray(array, N)) {
+  return ElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline auto ElementsAreArray(const Container& container)
+    -> decltype(ElementsAreArray(container.begin(), container.end())) {
+  return ElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline auto ElementsAreArray(::std::initializer_list<T> xs)
+    -> decltype(ElementsAreArray(xs.begin(), xs.end())) {
+  return ElementsAreArray(xs.begin(), xs.end());
+}
+
+// UnorderedElementsAreArray(iterator_first, iterator_last)
+// UnorderedElementsAreArray(pointer, count)
+// UnorderedElementsAreArray(array)
+// UnorderedElementsAreArray(container)
+// UnorderedElementsAreArray({ e1, e2, ..., en })
+//
+// UnorderedElementsAreArray() verifies that a bijective mapping onto a
+// collection of matchers exists.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+UnorderedElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::ExactMatch, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    const T* pointer, size_t count) {
+  return UnorderedElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    const T (&array)[N]) {
+  return UnorderedElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+UnorderedElementsAreArray(const Container& container) {
+  return UnorderedElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    ::std::initializer_list<T> xs) {
+  return UnorderedElementsAreArray(xs.begin(), xs.end());
+}
+
+// _ is a matcher that matches anything of any type.
+//
+// This definition is fine as:
+//
+//   1. The C++ standard permits using the name _ in a namespace that
+//      is not the global namespace or ::std.
+//   2. The AnythingMatcher class has no data member or constructor,
+//      so it's OK to create global variables of this type.
+//   3. c-style has approved of using _ in this case.
+const internal::AnythingMatcher _ = {};
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> A() {
+  return _;
+}
+
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> An() {
+  return _;
+}
+
+template <typename T, typename M>
+Matcher<T> internal::MatcherCastImpl<T, M>::CastImpl(
+    const M& value, std::false_type /* convertible_to_matcher */,
+    std::false_type /* convertible_to_T */) {
+  return Eq(value);
+}
+
+// Creates a polymorphic matcher that matches any NULL pointer.
+inline PolymorphicMatcher<internal::IsNullMatcher> IsNull() {
+  return MakePolymorphicMatcher(internal::IsNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any non-NULL pointer.
+// This is convenient as Not(NULL) doesn't compile (the compiler
+// thinks that that expression is comparing a pointer with an integer).
+inline PolymorphicMatcher<internal::NotNullMatcher> NotNull() {
+  return MakePolymorphicMatcher(internal::NotNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any argument that
+// references variable x.
+template <typename T>
+inline internal::RefMatcher<T&> Ref(T& x) {  // NOLINT
+  return internal::RefMatcher<T&>(x);
+}
+
+// Creates a polymorphic matcher that matches any NaN floating point.
+inline PolymorphicMatcher<internal::IsNanMatcher> IsNan() {
+  return MakePolymorphicMatcher(internal::IsNanMatcher());
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<double> DoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, false);
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, true);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> DoubleNear(double rhs,
+                                                      double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleNear(
+    double rhs, double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<float> FloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, false);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, true);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> FloatNear(float rhs,
+                                                    float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatNear(
+    float rhs, float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that points
+// to a value that matches inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointeeMatcher<InnerMatcher> Pointee(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointeeMatcher<InnerMatcher>(inner_matcher);
+}
+
+#if GTEST_HAS_RTTI
+// Creates a matcher that matches a pointer or reference that matches
+// inner_matcher when dynamic_cast<To> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+inline PolymorphicMatcher<internal::WhenDynamicCastToMatcher<To>>
+WhenDynamicCastTo(const Matcher<To>& inner_matcher) {
+  return MakePolymorphicMatcher(
+      internal::WhenDynamicCastToMatcher<To>(inner_matcher));
+}
+#endif  // GTEST_HAS_RTTI
+
+// Creates a matcher that matches an object whose given field matches
+// 'matcher'.  For example,
+//   Field(&Foo::number, Ge(5))
+// matches a Foo object x if and only if x.number >= 5.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<internal::FieldMatcher<Class, FieldType>> Field(
+    FieldType Class::*field, const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(internal::FieldMatcher<Class, FieldType>(
+      field, MatcherCast<const FieldType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Field(&Foo::bar, m)
+  // to compile where bar is an int32 and m is a matcher for int64.
+}
+
+// Same as Field() but also takes the name of the field to provide better error
+// messages.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<internal::FieldMatcher<Class, FieldType>> Field(
+    const std::string& field_name, FieldType Class::*field,
+    const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(internal::FieldMatcher<Class, FieldType>(
+      field_name, field, MatcherCast<const FieldType&>(matcher)));
+}
+
+// Creates a matcher that matches an object whose given property
+// matches 'matcher'.  For example,
+//   Property(&Foo::str, StartsWith("hi"))
+// matches a Foo object x if and only if x.str() starts with "hi".
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const>>
+Property(PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Property(&Foo::bar, m)
+  // to compile where bar() returns an int32 and m is a matcher for int64.
+}
+
+// Same as Property() above, but also takes the name of the property to provide
+// better error messages.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const>>
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// The same as above but for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const&>>
+Property(PropertyType (Class::*property)() const&,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Three-argument form for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const&>>
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const&,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Creates a matcher that matches an object if and only if the result of
+// applying a callable to x matches 'matcher'. For example,
+//   ResultOf(f, StartsWith("hi"))
+// matches a Foo object x if and only if f(x) starts with "hi".
+// `callable` parameter can be a function, function pointer, or a functor. It is
+// required to keep no state affecting the results of the calls on it and make
+// no assumptions about how many calls will be made. Any state it keeps must be
+// protected from the concurrent access.
+template <typename Callable, typename InnerMatcher>
+internal::ResultOfMatcher<Callable, InnerMatcher> ResultOf(
+    Callable callable, InnerMatcher matcher) {
+  return internal::ResultOfMatcher<Callable, InnerMatcher>(std::move(callable),
+                                                           std::move(matcher));
+}
+
+// Same as ResultOf() above, but also takes a description of the `callable`
+// result to provide better error messages.
+template <typename Callable, typename InnerMatcher>
+internal::ResultOfMatcher<Callable, InnerMatcher> ResultOf(
+    const std::string& result_description, Callable callable,
+    InnerMatcher matcher) {
+  return internal::ResultOfMatcher<Callable, InnerMatcher>(
+      result_description, std::move(callable), std::move(matcher));
+}
+
+// String matchers.
+
+// Matches a string equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, true));
+}
+
+// Matches a string not equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrCaseEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrCaseNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(internal::StrEqualityMatcher<std::string>(
+      std::string(str), false, false));
+}
+
+// Creates a matcher that matches any string, std::string, or C string
+// that contains the given substring.
+template <typename T = std::string>
+PolymorphicMatcher<internal::HasSubstrMatcher<std::string>> HasSubstr(
+    const internal::StringLike<T>& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::string>(std::string(substring)));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::StartsWithMatcher<std::string>> StartsWith(
+    const internal::StringLike<T>& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::string>(std::string(prefix)));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::EndsWithMatcher<std::string>> EndsWith(
+    const internal::StringLike<T>& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::string>(std::string(suffix)));
+}
+
+#if GTEST_HAS_STD_WSTRING
+// Wide string matchers.
+
+// Matches a string equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrEq(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, true));
+}
+
+// Matches a string not equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrNe(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrCaseEq(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrCaseNe(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, false));
+}
+
+// Creates a matcher that matches any ::wstring, std::wstring, or C wide string
+// that contains the given substring.
+inline PolymorphicMatcher<internal::HasSubstrMatcher<std::wstring>> HasSubstr(
+    const std::wstring& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::wstring>(substring));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+inline PolymorphicMatcher<internal::StartsWithMatcher<std::wstring>> StartsWith(
+    const std::wstring& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::wstring>(prefix));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+inline PolymorphicMatcher<internal::EndsWithMatcher<std::wstring>> EndsWith(
+    const std::wstring& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::wstring>(suffix));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field == the second field.
+inline internal::Eq2Matcher Eq() { return internal::Eq2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field >= the second field.
+inline internal::Ge2Matcher Ge() { return internal::Ge2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field > the second field.
+inline internal::Gt2Matcher Gt() { return internal::Gt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field <= the second field.
+inline internal::Le2Matcher Le() { return internal::Le2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field < the second field.
+inline internal::Lt2Matcher Lt() { return internal::Lt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field != the second field.
+inline internal::Ne2Matcher Ne() { return internal::Ne2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatEq() {
+  return internal::FloatingEq2Matcher<float>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleEq() {
+  return internal::FloatingEq2Matcher<double>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatEq() {
+  return internal::FloatingEq2Matcher<float>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleEq() {
+  return internal::FloatingEq2Matcher<double>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatNear(float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleNear(double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatNear(
+    float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error, true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleNear(
+    double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error, true);
+}
+
+// Creates a matcher that matches any value of type T that m doesn't
+// match.
+template <typename InnerMatcher>
+inline internal::NotMatcher<InnerMatcher> Not(InnerMatcher m) {
+  return internal::NotMatcher<InnerMatcher>(m);
+}
+
+// Returns a matcher that matches anything that satisfies the given
+// predicate.  The predicate can be any unary function or functor
+// whose return type can be implicitly converted to bool.
+template <typename Predicate>
+inline PolymorphicMatcher<internal::TrulyMatcher<Predicate>> Truly(
+    Predicate pred) {
+  return MakePolymorphicMatcher(internal::TrulyMatcher<Predicate>(pred));
+}
+
+// Returns a matcher that matches the container size. The container must
+// support both size() and size_type which all STL-like containers provide.
+// Note that the parameter 'size' can be a value of type size_type as well as
+// matcher. For instance:
+//   EXPECT_THAT(container, SizeIs(2));     // Checks container has 2 elements.
+//   EXPECT_THAT(container, SizeIs(Le(2));  // Checks container has at most 2.
+template <typename SizeMatcher>
+inline internal::SizeIsMatcher<SizeMatcher> SizeIs(
+    const SizeMatcher& size_matcher) {
+  return internal::SizeIsMatcher<SizeMatcher>(size_matcher);
+}
+
+// Returns a matcher that matches the distance between the container's begin()
+// iterator and its end() iterator, i.e. the size of the container. This matcher
+// can be used instead of SizeIs with containers such as std::forward_list which
+// do not implement size(). The container must provide const_iterator (with
+// valid iterator_traits), begin() and end().
+template <typename DistanceMatcher>
+inline internal::BeginEndDistanceIsMatcher<DistanceMatcher> BeginEndDistanceIs(
+    const DistanceMatcher& distance_matcher) {
+  return internal::BeginEndDistanceIsMatcher<DistanceMatcher>(distance_matcher);
+}
+
+// Returns a matcher that matches an equal container.
+// This matcher behaves like Eq(), but in the event of mismatch lists the
+// values that are included in one container but not the other. (Duplicate
+// values and order differences are not explained.)
+template <typename Container>
+inline PolymorphicMatcher<
+    internal::ContainerEqMatcher<typename std::remove_const<Container>::type>>
+ContainerEq(const Container& rhs) {
+  return MakePolymorphicMatcher(internal::ContainerEqMatcher<Container>(rhs));
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the given comparator, matches container_matcher.
+template <typename Comparator, typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<Comparator, ContainerMatcher> WhenSortedBy(
+    const Comparator& comparator, const ContainerMatcher& container_matcher) {
+  return internal::WhenSortedByMatcher<Comparator, ContainerMatcher>(
+      comparator, container_matcher);
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the < operator, matches container_matcher.
+template <typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<internal::LessComparator, ContainerMatcher>
+WhenSorted(const ContainerMatcher& container_matcher) {
+  return internal::WhenSortedByMatcher<internal::LessComparator,
+                                       ContainerMatcher>(
+      internal::LessComparator(), container_matcher);
+}
+
+// Matches an STL-style container or a native array that contains the
+// same number of elements as in rhs, where its i-th element and rhs's
+// i-th element (as a pair) satisfy the given pair matcher, for all i.
+// TupleMatcher must be able to be safely cast to Matcher<std::tuple<const
+// T1&, const T2&> >, where T1 and T2 are the types of elements in the
+// LHS container and the RHS container respectively.
+template <typename TupleMatcher, typename Container>
+inline internal::PointwiseMatcher<TupleMatcher,
+                                  typename std::remove_const<Container>::type>
+Pointwise(const TupleMatcher& tuple_matcher, const Container& rhs) {
+  return internal::PointwiseMatcher<TupleMatcher, Container>(tuple_matcher,
+                                                             rhs);
+}
+
+// Supports the Pointwise(m, {a, b, c}) syntax.
+template <typename TupleMatcher, typename T>
+inline internal::PointwiseMatcher<TupleMatcher, std::vector<T>> Pointwise(
+    const TupleMatcher& tuple_matcher, std::initializer_list<T> rhs) {
+  return Pointwise(tuple_matcher, std::vector<T>(rhs));
+}
+
+// UnorderedPointwise(pair_matcher, rhs) matches an STL-style
+// container or a native array that contains the same number of
+// elements as in rhs, where in some permutation of the container, its
+// i-th element and rhs's i-th element (as a pair) satisfy the given
+// pair matcher, for all i.  Tuple2Matcher must be able to be safely
+// cast to Matcher<std::tuple<const T1&, const T2&> >, where T1 and T2 are
+// the types of elements in the LHS container and the RHS container
+// respectively.
+//
+// This is like Pointwise(pair_matcher, rhs), except that the element
+// order doesn't matter.
+template <typename Tuple2Matcher, typename RhsContainer>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<
+        Tuple2Matcher,
+        typename internal::StlContainerView<
+            typename std::remove_const<RhsContainer>::type>::type::value_type>>
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   const RhsContainer& rhs_container) {
+  // RhsView allows the same code to handle RhsContainer being a
+  // STL-style container and it being a native C-style array.
+  typedef typename internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type Second;
+  const RhsStlContainer& rhs_stl_container =
+      RhsView::ConstReference(rhs_container);
+
+  // Create a matcher for each element in rhs_container.
+  ::std::vector<internal::BoundSecondMatcher<Tuple2Matcher, Second>> matchers;
+  for (auto it = rhs_stl_container.begin(); it != rhs_stl_container.end();
+       ++it) {
+    matchers.push_back(internal::MatcherBindSecond(tuple2_matcher, *it));
+  }
+
+  // Delegate the work to UnorderedElementsAreArray().
+  return UnorderedElementsAreArray(matchers);
+}
+
+// Supports the UnorderedPointwise(m, {a, b, c}) syntax.
+template <typename Tuple2Matcher, typename T>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<Tuple2Matcher, T>>
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   std::initializer_list<T> rhs) {
+  return UnorderedPointwise(tuple2_matcher, std::vector<T>(rhs));
+}
+
+// Matches an STL-style container or a native array that contains at
+// least one element matching the given value or matcher.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   page_ids.insert(3);
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Contains(1));
+//   EXPECT_THAT(page_ids, Contains(Gt(2)));
+//   EXPECT_THAT(page_ids, Not(Contains(4)));  // See below for Times(0)
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   EXPECT_THAT(page_lengths,
+//               Contains(::std::pair<const int, size_t>(1, 100)));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Contains(Eq(::std::string("tom"))));
+//
+// The matcher supports a modifier `Times` that allows to check for arbitrary
+// occurrences including testing for absence with Times(0).
+//
+// Examples:
+//   ::std::vector<int> ids;
+//   ids.insert(1);
+//   ids.insert(1);
+//   ids.insert(3);
+//   EXPECT_THAT(ids, Contains(1).Times(2));      // 1 occurs 2 times
+//   EXPECT_THAT(ids, Contains(2).Times(0));      // 2 is not present
+//   EXPECT_THAT(ids, Contains(3).Times(Ge(1)));  // 3 occurs at least once
+
+template <typename M>
+inline internal::ContainsMatcher<M> Contains(M matcher) {
+  return internal::ContainsMatcher<M>(matcher);
+}
+
+// IsSupersetOf(iterator_first, iterator_last)
+// IsSupersetOf(pointer, count)
+// IsSupersetOf(array)
+// IsSupersetOf(container)
+// IsSupersetOf({e1, e2, ..., en})
+//
+// IsSupersetOf() verifies that a surjective partial mapping onto a collection
+// of matchers exists. In other words, a container matches
+// IsSupersetOf({e1, ..., en}) if and only if there is a permutation
+// {y1, ..., yn} of some of the container's elements where y1 matches e1,
+// ..., and yn matches en. Obviously, the size of the container must be >= n
+// in order to have a match. Examples:
+//
+// - {1, 2, 3} matches IsSupersetOf({Ge(3), Ne(0)}), as 3 matches Ge(3) and
+//   1 matches Ne(0).
+// - {1, 2} doesn't match IsSupersetOf({Eq(1), Lt(2)}), even though 1 matches
+//   both Eq(1) and Lt(2). The reason is that different matchers must be used
+//   for elements in different slots of the container.
+// - {1, 1, 2} matches IsSupersetOf({Eq(1), Lt(2)}), as (the first) 1 matches
+//   Eq(1) and (the second) 1 matches Lt(2).
+// - {1, 2, 3} matches IsSupersetOf(Gt(1), Gt(1)), as 2 matches (the first)
+//   Gt(1) and 3 matches (the second) Gt(1).
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSupersetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Superset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T* pointer, size_t count) {
+  return IsSupersetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T (&array)[N]) {
+  return IsSupersetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSupersetOf(const Container& container) {
+  return IsSupersetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSupersetOf(xs.begin(), xs.end());
+}
+
+// IsSubsetOf(iterator_first, iterator_last)
+// IsSubsetOf(pointer, count)
+// IsSubsetOf(array)
+// IsSubsetOf(container)
+// IsSubsetOf({e1, e2, ..., en})
+//
+// IsSubsetOf() verifies that an injective mapping onto a collection of matchers
+// exists.  In other words, a container matches IsSubsetOf({e1, ..., en}) if and
+// only if there is a subset of matchers {m1, ..., mk} which would match the
+// container using UnorderedElementsAre.  Obviously, the size of the container
+// must be <= n in order to have a match. Examples:
+//
+// - {1} matches IsSubsetOf({Gt(0), Lt(0)}), as 1 matches Gt(0).
+// - {1, -1} matches IsSubsetOf({Lt(0), Gt(0)}), as 1 matches Gt(0) and -1
+//   matches Lt(0).
+// - {1, 2} doesn't matches IsSubsetOf({Gt(0), Lt(0)}), even though 1 and 2 both
+//   match Gt(0). The reason is that different matchers must be used for
+//   elements in different slots of the container.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSubsetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Subset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T* pointer, size_t count) {
+  return IsSubsetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T (&array)[N]) {
+  return IsSubsetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSubsetOf(const Container& container) {
+  return IsSubsetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSubsetOf(xs.begin(), xs.end());
+}
+
+// Matches an STL-style container or a native array that contains only
+// elements matching the given value or matcher.
+//
+// Each(m) is semantically equivalent to `Not(Contains(Not(m)))`. Only
+// the messages are different.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   // Each(m) matches an empty container, regardless of what m is.
+//   EXPECT_THAT(page_ids, Each(Eq(1)));
+//   EXPECT_THAT(page_ids, Each(Eq(77)));
+//
+//   page_ids.insert(3);
+//   EXPECT_THAT(page_ids, Each(Gt(0)));
+//   EXPECT_THAT(page_ids, Not(Each(Gt(4))));
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Not(Each(Lt(2))));
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   page_lengths[2] = 200;
+//   page_lengths[3] = 300;
+//   EXPECT_THAT(page_lengths, Not(Each(Pair(1, 100))));
+//   EXPECT_THAT(page_lengths, Each(Key(Le(3))));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Not(Each(Eq(::std::string("tom")))));
+template <typename M>
+inline internal::EachMatcher<M> Each(M matcher) {
+  return internal::EachMatcher<M>(matcher);
+}
+
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename M>
+inline internal::KeyMatcher<M> Key(M inner_matcher) {
+  return internal::KeyMatcher<M>(inner_matcher);
+}
+
+// Pair(first_matcher, second_matcher) matches a std::pair whose 'first' field
+// matches first_matcher and whose 'second' field matches second_matcher.  For
+// example, EXPECT_THAT(map_type, ElementsAre(Pair(Ge(5), "foo"))) can be used
+// to match a std::map<int, string> that contains exactly one element whose key
+// is >= 5 and whose value equals "foo".
+template <typename FirstMatcher, typename SecondMatcher>
+inline internal::PairMatcher<FirstMatcher, SecondMatcher> Pair(
+    FirstMatcher first_matcher, SecondMatcher second_matcher) {
+  return internal::PairMatcher<FirstMatcher, SecondMatcher>(first_matcher,
+                                                            second_matcher);
+}
+
+namespace no_adl {
+// Conditional() creates a matcher that conditionally uses either the first or
+// second matcher provided. For example, we could create an `equal if, and only
+// if' matcher using the Conditional wrapper as follows:
+//
+//   EXPECT_THAT(result, Conditional(condition, Eq(expected), Ne(expected)));
+template <typename MatcherTrue, typename MatcherFalse>
+internal::ConditionalMatcher<MatcherTrue, MatcherFalse> Conditional(
+    bool condition, MatcherTrue matcher_true, MatcherFalse matcher_false) {
+  return internal::ConditionalMatcher<MatcherTrue, MatcherFalse>(
+      condition, std::move(matcher_true), std::move(matcher_false));
+}
+
+// FieldsAre(matchers...) matches piecewise the fields of compatible structs.
+// These include those that support `get<I>(obj)`, and when structured bindings
+// are enabled any class that supports them.
+// In particular, `std::tuple`, `std::pair`, `std::array` and aggregate types.
+template <typename... M>
+internal::FieldsAreMatcher<typename std::decay<M>::type...> FieldsAre(
+    M&&... matchers) {
+  return internal::FieldsAreMatcher<typename std::decay<M>::type...>(
+      std::forward<M>(matchers)...);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointerMatcher<InnerMatcher> Pointer(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointerMatcher<InnerMatcher>(inner_matcher);
+}
+
+// Creates a matcher that matches an object that has an address that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::AddressMatcher<InnerMatcher> Address(
+    const InnerMatcher& inner_matcher) {
+  return internal::AddressMatcher<InnerMatcher>(inner_matcher);
+}
+
+// Matches a base64 escaped string, when the unescaped string matches the
+// internal matcher.
+template <typename MatcherType>
+internal::WhenBase64UnescapedMatcher WhenBase64Unescaped(
+    const MatcherType& internal_matcher) {
+  return internal::WhenBase64UnescapedMatcher(internal_matcher);
+}
+}  // namespace no_adl
+
+// Returns a predicate that is satisfied by anything that matches the
+// given matcher.
+template <typename M>
+inline internal::MatcherAsPredicate<M> Matches(M matcher) {
+  return internal::MatcherAsPredicate<M>(matcher);
+}
+
+// Returns true if and only if the value matches the matcher.
+template <typename T, typename M>
+inline bool Value(const T& value, M matcher) {
+  return testing::Matches(matcher)(value);
+}
+
+// Matches the value against the given matcher and explains the match
+// result to listener.
+template <typename T, typename M>
+inline bool ExplainMatchResult(M matcher, const T& value,
+                               MatchResultListener* listener) {
+  return SafeMatcherCast<const T&>(matcher).MatchAndExplain(value, listener);
+}
+
+// Returns a string representation of the given matcher.  Useful for description
+// strings of matchers defined using MATCHER_P* macros that accept matchers as
+// their arguments.  For example:
+//
+// MATCHER_P(XAndYThat, matcher,
+//           "X that " + DescribeMatcher<int>(matcher, negation) +
+//               (negation ? " or" : " and") + " Y that " +
+//               DescribeMatcher<double>(matcher, negation)) {
+//   return ExplainMatchResult(matcher, arg.x(), result_listener) &&
+//          ExplainMatchResult(matcher, arg.y(), result_listener);
+// }
+template <typename T, typename M>
+std::string DescribeMatcher(const M& matcher, bool negation = false) {
+  ::std::stringstream ss;
+  Matcher<T> monomorphic_matcher = SafeMatcherCast<T>(matcher);
+  if (negation) {
+    monomorphic_matcher.DescribeNegationTo(&ss);
+  } else {
+    monomorphic_matcher.DescribeTo(&ss);
+  }
+  return ss.str();
+}
+
+template <typename... Args>
+internal::ElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+ElementsAre(const Args&... matchers) {
+  return internal::ElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+template <typename... Args>
+internal::UnorderedElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+UnorderedElementsAre(const Args&... matchers) {
+  return internal::UnorderedElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+// Define variadic matcher versions.
+template <typename... Args>
+internal::AllOfMatcher<typename std::decay<const Args&>::type...> AllOf(
+    const Args&... matchers) {
+  return internal::AllOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+template <typename... Args>
+internal::AnyOfMatcher<typename std::decay<const Args&>::type...> AnyOf(
+    const Args&... matchers) {
+  return internal::AnyOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+// AnyOfArray(array)
+// AnyOfArray(pointer, count)
+// AnyOfArray(container)
+// AnyOfArray({ e1, e2, ..., en })
+// AnyOfArray(iterator_first, iterator_last)
+//
+// AnyOfArray() verifies whether a given value matches any member of a
+// collection of matchers.
+//
+// AllOfArray(array)
+// AllOfArray(pointer, count)
+// AllOfArray(container)
+// AllOfArray({ e1, e2, ..., en })
+// AllOfArray(iterator_first, iterator_last)
+//
+// AllOfArray() verifies whether a given value matches all members of a
+// collection of matchers.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::AnyOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AnyOfArray(Iter first, Iter last) {
+  return internal::AnyOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename Iter>
+inline internal::AllOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AllOfArray(Iter first, Iter last) {
+  return internal::AllOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T* ptr, size_t count) {
+  return AnyOfArray(ptr, ptr + count);
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T* ptr, size_t count) {
+  return AllOfArray(ptr, ptr + count);
+}
+
+template <typename T, size_t N>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T (&array)[N]) {
+  return AnyOfArray(array, N);
+}
+
+template <typename T, size_t N>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T (&array)[N]) {
+  return AllOfArray(array, N);
+}
+
+template <typename Container>
+inline internal::AnyOfArrayMatcher<typename Container::value_type> AnyOfArray(
+    const Container& container) {
+  return AnyOfArray(container.begin(), container.end());
+}
+
+template <typename Container>
+inline internal::AllOfArrayMatcher<typename Container::value_type> AllOfArray(
+    const Container& container) {
+  return AllOfArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(
+    ::std::initializer_list<T> xs) {
+  return AnyOfArray(xs.begin(), xs.end());
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(
+    ::std::initializer_list<T> xs) {
+  return AllOfArray(xs.begin(), xs.end());
+}
+
+// Args<N1, N2, ..., Nk>(a_matcher) matches a tuple if the selected
+// fields of it matches a_matcher.  C++ doesn't support default
+// arguments for function templates, so we have to overload it.
+template <size_t... k, typename InnerMatcher>
+internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...> Args(
+    InnerMatcher&& matcher) {
+  return internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...>(
+      std::forward<InnerMatcher>(matcher));
+}
+
+// AllArgs(m) is a synonym of m.  This is useful in
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(AllArgs(Eq()));
+//
+// which is easier to read than
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(Eq());
+template <typename InnerMatcher>
+inline InnerMatcher AllArgs(const InnerMatcher& matcher) {
+  return matcher;
+}
+
+// Returns a matcher that matches the value of an optional<> type variable.
+// The matcher implementation only uses '!arg' and requires that the optional<>
+// type has a 'value_type' member type and that '*arg' is of type 'value_type'
+// and is printable using 'PrintToString'. It is compatible with
+// std::optional/std::experimental::optional.
+// Note that to compare an optional type variable against nullopt you should
+// use Eq(nullopt) and not Eq(Optional(nullopt)). The latter implies that the
+// optional value contains an optional itself.
+template <typename ValueMatcher>
+inline internal::OptionalMatcher<ValueMatcher> Optional(
+    const ValueMatcher& value_matcher) {
+  return internal::OptionalMatcher<ValueMatcher>(value_matcher);
+}
+
+// Returns a matcher that matches the value of a absl::any type variable.
+template <typename T>
+PolymorphicMatcher<internal::any_cast_matcher::AnyCastMatcher<T>> AnyWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::any_cast_matcher::AnyCastMatcher<T>(matcher));
+}
+
+// Returns a matcher that matches the value of a variant<> type variable.
+// The matcher implementation uses ADL to find the holds_alternative and get
+// functions.
+// It is compatible with std::variant.
+template <typename T>
+PolymorphicMatcher<internal::variant_matcher::VariantMatcher<T>> VariantWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::variant_matcher::VariantMatcher<T>(matcher));
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Anything inside the `internal` namespace is internal to the implementation
+// and must not be used in user code!
+namespace internal {
+
+class WithWhatMatcherImpl {
+ public:
+  WithWhatMatcherImpl(Matcher<std::string> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "contains .what() that ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "contains .what() that does not ";
+    matcher_.DescribeTo(os);
+  }
+
+  template <typename Err>
+  bool MatchAndExplain(const Err& err, MatchResultListener* listener) const {
+    *listener << "which contains .what() (of value = " << err.what()
+              << ") that ";
+    return matcher_.MatchAndExplain(err.what(), listener);
+  }
+
+ private:
+  const Matcher<std::string> matcher_;
+};
+
+inline PolymorphicMatcher<WithWhatMatcherImpl> WithWhat(
+    Matcher<std::string> m) {
+  return MakePolymorphicMatcher(WithWhatMatcherImpl(std::move(m)));
+}
+
+template <typename Err>
+class ExceptionMatcherImpl {
+  class NeverThrown {
+   public:
+    const char* what() const noexcept {
+      return "this exception should never be thrown";
+    }
+  };
+
+  // If the matchee raises an exception of a wrong type, we'd like to
+  // catch it and print its message and type. To do that, we add an additional
+  // catch clause:
+  //
+  //     try { ... }
+  //     catch (const Err&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // However, if the `Err` itself is `std::exception`, we'd end up with two
+  // identical `catch` clauses:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // This can cause a warning or an error in some compilers. To resolve
+  // the issue, we use a fake error type whenever `Err` is `std::exception`:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const NeverThrown&) { /* exception of a wrong type */ }
+  using DefaultExceptionType = typename std::conditional<
+      std::is_same<typename std::remove_cv<
+                       typename std::remove_reference<Err>::type>::type,
+                   std::exception>::value,
+      const NeverThrown&, const std::exception&>::type;
+
+ public:
+  ExceptionMatcherImpl(Matcher<const Err&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "throws an exception which is a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "throws an exception which is not a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(T&& x, MatchResultListener* listener) const {
+    try {
+      (void)(std::forward<T>(x)());
+    } catch (const Err& err) {
+      *listener << "throws an exception which is a " << GetTypeName<Err>();
+      *listener << " ";
+      return matcher_.MatchAndExplain(err, listener);
+    } catch (DefaultExceptionType err) {
+#if GTEST_HAS_RTTI
+      *listener << "throws an exception of type " << GetTypeName(typeid(err));
+      *listener << " ";
+#else
+      *listener << "throws an std::exception-derived type ";
+#endif
+      *listener << "with description \"" << err.what() << "\"";
+      return false;
+    } catch (...) {
+      *listener << "throws an exception of an unknown type";
+      return false;
+    }
+
+    *listener << "does not throw any exception";
+    return false;
+  }
+
+ private:
+  const Matcher<const Err&> matcher_;
+};
+
+}  // namespace internal
+
+// Throws()
+// Throws(exceptionMatcher)
+// ThrowsMessage(messageMatcher)
+//
+// This matcher accepts a callable and verifies that when invoked, it throws
+// an exception with the given type and properties.
+//
+// Examples:
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>());
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>(
+//           Property(&std::runtime_error::what, HasSubstr("message"))));
+
+template <typename Err>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws() {
+  return MakePolymorphicMatcher(
+      internal::ExceptionMatcherImpl<Err>(A<const Err&>()));
+}
+
+template <typename Err, typename ExceptionMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws(
+    const ExceptionMatcher& exception_matcher) {
+  // Using matcher cast allows users to pass a matcher of a more broad type.
+  // For example user may want to pass Matcher<std::exception>
+  // to Throws<std::runtime_error>, or Matcher<int64> to Throws<int32>.
+  return MakePolymorphicMatcher(internal::ExceptionMatcherImpl<Err>(
+      SafeMatcherCast<const Err&>(exception_matcher)));
+}
+
+template <typename Err, typename MessageMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> ThrowsMessage(
+    MessageMatcher&& message_matcher) {
+  static_assert(std::is_base_of<std::exception, Err>::value,
+                "expected an std::exception-derived type");
+  return Throws<Err>(internal::WithWhat(
+      MatcherCast<std::string>(std::forward<MessageMatcher>(message_matcher))));
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// These macros allow using matchers to check values in Google Test
+// tests.  ASSERT_THAT(value, matcher) and EXPECT_THAT(value, matcher)
+// succeed if and only if the value matches the matcher.  If the assertion
+// fails, the value and the description of the matcher will be printed.
+#define ASSERT_THAT(value, matcher) \
+  ASSERT_PRED_FORMAT1(              \
+      ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+#define EXPECT_THAT(value, matcher) \
+  EXPECT_PRED_FORMAT1(              \
+      ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+
+// MATCHER* macros itself are listed below.
+#define MATCHER(name, description)                                             \
+  class name##Matcher                                                          \
+      : public ::testing::internal::MatcherBaseImpl<name##Matcher> {           \
+   public:                                                                     \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      gmock_Impl() {}                                                          \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        /* NOLINTNEXTLINE readability-redundant-string-init */                 \
+        ::std::string gmock_description = (description);                       \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(negation, #name,  \
+                                                             {}, {});          \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  GTEST_ATTRIBUTE_UNUSED_ inline name##Matcher name() { return {}; }           \
+  template <typename arg_type>                                                 \
+  bool name##Matcher::gmock_Impl<arg_type>::MatchAndExplain(                   \
+      const arg_type& arg,                                                     \
+      ::testing::MatchResultListener* result_listener GTEST_ATTRIBUTE_UNUSED_) \
+      const
+
+#define MATCHER_P(name, p0, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP, description, (#p0), (p0))
+#define MATCHER_P2(name, p0, p1, description)                            \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP2, description, (#p0, #p1), \
+                         (p0, p1))
+#define MATCHER_P3(name, p0, p1, p2, description)                             \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP3, description, (#p0, #p1, #p2), \
+                         (p0, p1, p2))
+#define MATCHER_P4(name, p0, p1, p2, p3, description)        \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP4, description, \
+                         (#p0, #p1, #p2, #p3), (p0, p1, p2, p3))
+#define MATCHER_P5(name, p0, p1, p2, p3, p4, description)    \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP5, description, \
+                         (#p0, #p1, #p2, #p3, #p4), (p0, p1, p2, p3, p4))
+#define MATCHER_P6(name, p0, p1, p2, p3, p4, p5, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP6, description,  \
+                         (#p0, #p1, #p2, #p3, #p4, #p5),      \
+                         (p0, p1, p2, p3, p4, p5))
+#define MATCHER_P7(name, p0, p1, p2, p3, p4, p5, p6, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP7, description,      \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6),     \
+                         (p0, p1, p2, p3, p4, p5, p6))
+#define MATCHER_P8(name, p0, p1, p2, p3, p4, p5, p6, p7, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP8, description,          \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7),    \
+                         (p0, p1, p2, p3, p4, p5, p6, p7))
+#define MATCHER_P9(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP9, description,              \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7, #p8),   \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8))
+#define MATCHER_P10(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP10, description,                  \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7, #p8, #p9),   \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8, p9))
+
+#define GMOCK_INTERNAL_MATCHER(name, full_name, description, arg_names, args)  \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  class full_name : public ::testing::internal::MatcherBaseImpl<               \
+                        full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>> { \
+   public:                                                                     \
+    using full_name::MatcherBaseImpl::MatcherBaseImpl;                         \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      explicit gmock_Impl(GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args))          \
+          : GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) {}                       \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+      GMOCK_INTERNAL_MATCHER_MEMBERS(args)                                     \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        ::std::string gmock_description = (description);                       \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(                  \
+            negation, #name, {GMOCK_PP_REMOVE_PARENS(arg_names)},              \
+            ::testing::internal::UniversalTersePrintTupleFieldsToStrings(      \
+                ::std::tuple<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(        \
+                    GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args))));             \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  inline full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)> name(             \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args)) {                            \
+    return full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(                \
+        GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args));                              \
+  }                                                                            \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  template <typename arg_type>                                                 \
+  bool full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>::gmock_Impl<        \
+      arg_type>::MatchAndExplain(const arg_type& arg,                          \
+                                 ::testing::MatchResultListener*               \
+                                     result_listener GTEST_ATTRIBUTE_UNUSED_)  \
+      const
+
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args) \
+  GMOCK_PP_TAIL(                                     \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM(i_unused, data_unused, arg) \
+  , typename arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TYPE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAM(i_unused, data_unused, arg) \
+  , arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args) \
+  GMOCK_PP_TAIL(dummy_first GMOCK_PP_FOR_EACH(     \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARG(i, data_unused, arg) \
+  , arg##_type gmock_p##i
+
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_FORWARD_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARG(i, data_unused, arg) \
+  , arg(::std::forward<arg##_type>(gmock_p##i))
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS(args) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER, , args)
+#define GMOCK_INTERNAL_MATCHER_MEMBER(i_unused, data_unused, arg) \
+  const arg##_type arg;
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_MEMBER_USAGE(i_unused, data_unused, arg) , arg
+
+#define GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_ARG_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_ARG_USAGE(i, data_unused, arg_unused) \
+  , gmock_p##i
+
+// To prevent ADL on certain functions we put them on a separate namespace.
+using namespace no_adl;  // NOLINT
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251 5046
+
+// Include any custom callback matchers added by the local installation.
+// We must include this header at the end to make sure it can use the
+// declarations from this file.
+#include "gmock/internal/custom/gmock-matchers.h"
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_