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 // 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);
 }
 #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[] = {"", (*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_