googletest/googlemock/include/gmock/gmock-actions.h

// Copyright 2007, Google Inc.
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//
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Google Mock - a framework for writing C++ mock classes.
//
// The ACTION* family of macros can be used in a namespace scope to
// define custom actions easily.  The syntax:
//
//   ACTION(name) { statements; }
//
// will define an action with the given name that executes the
// statements.  The value returned by the statements will be used as
// the return value of the action.  Inside the statements, you can
// refer to the K-th (0-based) argument of the mock function by
// 'argK', and refer to its type by 'argK_type'.  For example:
//
//   ACTION(IncrementArg1) {
//     arg1_type temp = arg1;
//     return ++(*temp);
//   }
//
// allows you to write
//
//   ...WillOnce(IncrementArg1());
//
// You can also refer to the entire argument tuple and its type by
// 'args' and 'args_type', and refer to the mock function type and its
// return type by 'function_type' and 'return_type'.
//
// Note that you don't need to specify the types of the mock function
// arguments.  However rest assured that your code is still type-safe:
// you'll get a compiler error if *arg1 doesn't support the ++
// operator, or if the type of ++(*arg1) isn't compatible with the
// mock function's return type, for example.
//
// Sometimes you'll want to parameterize the action.   For that you can use
// another macro:
//
//   ACTION_P(name, param_name) { statements; }
//
// For example:
//
//   ACTION_P(Add, n) { return arg0 + n; }
//
// will allow you to write:
//
//   ...WillOnce(Add(5));
//
// Note that you don't need to provide the type of the parameter
// either.  If you need to reference the type of a parameter named
// 'foo', you can write 'foo_type'.  For example, in the body of
// ACTION_P(Add, n) above, you can write 'n_type' to refer to the type
// of 'n'.
//
// We also provide ACTION_P2, ACTION_P3, ..., up to ACTION_P10 to support
// multi-parameter actions.
//
// For the purpose of typing, you can view
//
//   ACTION_Pk(Foo, p1, ..., pk) { ... }
//
// as shorthand for
//
//   template <typename p1_type, ..., typename pk_type>
//   FooActionPk<p1_type, ..., pk_type> Foo(p1_type p1, ..., pk_type pk) { ... }
//
// In particular, you can provide the template type arguments
// explicitly when invoking Foo(), as in Foo<long, bool>(5, false);
// although usually you can rely on the compiler to infer the types
// for you automatically.  You can assign the result of expression
// Foo(p1, ..., pk) to a variable of type FooActionPk<p1_type, ...,
// pk_type>.  This can be useful when composing actions.
//
// You can also overload actions with different numbers of parameters:
//
//   ACTION_P(Plus, a) { ... }
//   ACTION_P2(Plus, a, b) { ... }
//
// While it's tempting to always use the ACTION* macros when defining
// a new action, you should also consider implementing ActionInterface
// or using MakePolymorphicAction() instead, especially if you need to
// use the action a lot.  While these approaches require more work,
// they give you more control on the types of the mock function
// arguments and the action parameters, which in general leads to
// better compiler error messages that pay off in the long run.  They
// also allow overloading actions based on parameter types (as opposed
// to just based on the number of parameters).
//
// CAVEAT:
//
// ACTION*() can only be used in a namespace scope as templates cannot be
// declared inside of a local class.
// Users can, however, define any local functors (e.g. a lambda) that
// can be used as actions.
//
// MORE INFORMATION:
//
// To learn more about using these macros, please search for 'ACTION' on
// https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md

// IWYU pragma: private, include "gmock/gmock.h"
// IWYU pragma: friend gmock/.*

#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_

#ifndef _WIN32_WCE
#include <errno.h>
#endif

#include <algorithm>
#include <functional>
#include <memory>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>

#include "gmock/internal/gmock-internal-utils.h"
#include "gmock/internal/gmock-port.h"
#include "gmock/internal/gmock-pp.h"

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4100)
#endif

namespace testing {

// To implement an action Foo, define:
//   1. a class FooAction that implements the ActionInterface interface, and
//   2. a factory function that creates an Action object from a
//      const FooAction*.
//
// The two-level delegation design follows that of Matcher, providing
// consistency for extension developers.  It also eases ownership
// management as Action objects can now be copied like plain values.

namespace internal {

// BuiltInDefaultValueGetter<T, true>::Get() returns a
// default-constructed T value.  BuiltInDefaultValueGetter<T,
// false>::Get() crashes with an error.
//
// This primary template is used when kDefaultConstructible is true.
template <typename T, bool kDefaultConstructible>
struct BuiltInDefaultValueGetter {
  static T Get() { return T(); }
};
template <typename T>
struct BuiltInDefaultValueGetter<T, false> {
  static T Get() {
    Assert(false, __FILE__, __LINE__,
           "Default action undefined for the function return type.");
    return internal::Invalid<T>();
    // The above statement will never be reached, but is required in
    // order for this function to compile.
  }
};

// BuiltInDefaultValue<T>::Get() returns the "built-in" default value
// for type T, which is NULL when T is a raw pointer type, 0 when T is
// a numeric type, false when T is bool, or "" when T is string or
// std::string.  In addition, in C++11 and above, it turns a
// default-constructed T value if T is default constructible.  For any
// other type T, the built-in default T value is undefined, and the
// function will abort the process.
template <typename T>
class BuiltInDefaultValue {
 public:
  // This function returns true if and only if type T has a built-in default
  // value.
  static bool Exists() { return ::std::is_default_constructible<T>::value; }

  static T Get() {
    return BuiltInDefaultValueGetter<
        T, ::std::is_default_constructible<T>::value>::Get();
  }
};

// This partial specialization says that we use the same built-in
// default value for T and const T.
template <typename T>
class BuiltInDefaultValue<const T> {
 public:
  static bool Exists() { return BuiltInDefaultValue<T>::Exists(); }
  static T Get() { return BuiltInDefaultValue<T>::Get(); }
};

// This partial specialization defines the default values for pointer
// types.
template <typename T>
class BuiltInDefaultValue<T*> {
 public:
  static bool Exists() { return true; }
  static T* Get() { return nullptr; }
};

// The following specializations define the default values for
// specific types we care about.
#define GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(type, value) \
  template <>                                                     \
  class BuiltInDefaultValue<type> {                               \
   public:                                                        \
    static bool Exists() { return true; }                         \
    static type Get() { return value; }                           \
  }

GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(void, );  // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(::std::string, "");
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(bool, false);
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned char, '\0');
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed char, '\0');
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(char, '\0');

// There's no need for a default action for signed wchar_t, as that
// type is the same as wchar_t for gcc, and invalid for MSVC.
//
// There's also no need for a default action for unsigned wchar_t, as
// that type is the same as unsigned int for gcc, and invalid for
// MSVC.
#if GMOCK_WCHAR_T_IS_NATIVE_
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(wchar_t, 0U);  // NOLINT
#endif

GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned short, 0U);  // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed short, 0);     // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned int, 0U);
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed int, 0);
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long, 0UL);     // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long, 0L);        // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long long, 0);  // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long long, 0);    // NOLINT
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(float, 0);
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(double, 0);

#undef GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_

// Partial implementations of metaprogramming types from the standard library
// not available in C++11.

template <typename P>
struct negation
    // NOLINTNEXTLINE
    : std::integral_constant<bool, bool(!P::value)> {};

// Base case: with zero predicates the answer is always true.
template <typename...>
struct conjunction : std::true_type {};

// With a single predicate, the answer is that predicate.
template <typename P1>
struct conjunction<P1> : P1 {};

// With multiple predicates the answer is the first predicate if that is false,
// and we recurse otherwise.
template <typename P1, typename... Ps>
struct conjunction<P1, Ps...>
    : std::conditional<bool(P1::value), conjunction<Ps...>, P1>::type {};

template <typename...>
struct disjunction : std::false_type {};

template <typename P1>
struct disjunction<P1> : P1 {};

template <typename P1, typename... Ps>
struct disjunction<P1, Ps...>
    // NOLINTNEXTLINE
    : std::conditional<!bool(P1::value), disjunction<Ps...>, P1>::type {};

template <typename...>
using void_t = void;

// Like std::invoke_result_t from C++17, but works only for objects with call
// operators (not e.g. member function pointers, which we don't need specific
// support for in OnceAction because std::function deals with them).
template <typename F, typename... Args>
using call_result_t = decltype(std::declval<F>()(std::declval<Args>()...));

template <typename Void, typename R, typename F, typename... Args>
struct is_callable_r_impl : std::false_type {};

// Specialize the struct for those template arguments where call_result_t is
// well-formed. When it's not, the generic template above is chosen, resulting
// in std::false_type.
template <typename R, typename F, typename... Args>
struct is_callable_r_impl<void_t<call_result_t<F, Args...>>, R, F, Args...>
    : std::conditional<
          std::is_same<R, void>::value,  //
          std::true_type,                //
          std::is_convertible<call_result_t<F, Args...>, R>>::type {};

// Like std::is_invocable_r from C++17, but works only for objects with call
// operators. See the note on call_result_t.
template <typename R, typename F, typename... Args>
using is_callable_r = is_callable_r_impl<void, R, F, Args...>;

}  // namespace internal

// When an unexpected function call is encountered, Google Mock will
// let it return a default value if the user has specified one for its
// return type, or if the return type has a built-in default value;
// otherwise Google Mock won't know what value to return and will have
// to abort the process.
//
// The DefaultValue<T> class allows a user to specify the
// default value for a type T that is both copyable and publicly
// destructible (i.e. anything that can be used as a function return
// type).  The usage is:
//
//   // Sets the default value for type T to be foo.
//   DefaultValue<T>::Set(foo);
template <typename T>
class DefaultValue {
 public:
  // Sets the default value for type T; requires T to be
  // copy-constructable and have a public destructor.
  static void Set(T x) {
    delete producer_;
    producer_ = new FixedValueProducer(x);
  }

  // Provides a factory function to be called to generate the default value.
  // This method can be used even if T is only move-constructible, but it is not
  // limited to that case.
  typedef T (*FactoryFunction)();
  static void SetFactory(FactoryFunction factory) {
    delete producer_;
    producer_ = new FactoryValueProducer(factory);
  }

  // Unsets the default value for type T.
  static void Clear() {
    delete producer_;
    producer_ = nullptr;
  }

  // Returns true if and only if the user has set the default value for type T.
  static bool IsSet() { return producer_ != nullptr; }

  // Returns true if T has a default return value set by the user or there
  // exists a built-in default value.
  static bool Exists() {
    return IsSet() || internal::BuiltInDefaultValue<T>::Exists();
  }

  // Returns the default value for type T if the user has set one;
  // otherwise returns the built-in default value. Requires that Exists()
  // is true, which ensures that the return value is well-defined.
  static T Get() {
    return producer_ == nullptr ? internal::BuiltInDefaultValue<T>::Get()
                                : producer_->Produce();
  }

 private:
  class ValueProducer {
   public:
    virtual ~ValueProducer() {}
    virtual T Produce() = 0;
  };

  class FixedValueProducer : public ValueProducer {
   public:
    explicit FixedValueProducer(T value) : value_(value) {}
    T Produce() override { return value_; }

   private:
    const T value_;
    GTEST_DISALLOW_COPY_AND_ASSIGN_(FixedValueProducer);
  };

  class FactoryValueProducer : public ValueProducer {
   public:
    explicit FactoryValueProducer(FactoryFunction factory)
        : factory_(factory) {}
    T Produce() override { return factory_(); }

   private:
    const FactoryFunction factory_;
    GTEST_DISALLOW_COPY_AND_ASSIGN_(FactoryValueProducer);
  };

  static ValueProducer* producer_;
};

// This partial specialization allows a user to set default values for
// reference types.
template <typename T>
class DefaultValue<T&> {
 public:
  // Sets the default value for type T&.
  static void Set(T& x) {  // NOLINT
    address_ = &x;
  }

  // Unsets the default value for type T&.
  static void Clear() { address_ = nullptr; }

  // Returns true if and only if the user has set the default value for type T&.
  static bool IsSet() { return address_ != nullptr; }

  // Returns true if T has a default return value set by the user or there
  // exists a built-in default value.
  static bool Exists() {
    return IsSet() || internal::BuiltInDefaultValue<T&>::Exists();
  }

  // Returns the default value for type T& if the user has set one;
  // otherwise returns the built-in default value if there is one;
  // otherwise aborts the process.
  static T& Get() {
    return address_ == nullptr ? internal::BuiltInDefaultValue<T&>::Get()
                               : *address_;
  }

 private:
  static T* address_;
};

// This specialization allows DefaultValue<void>::Get() to
// compile.
template <>
class DefaultValue<void> {
 public:
  static bool Exists() { return true; }
  static void Get() {}
};

// Points to the user-set default value for type T.
template <typename T>
typename DefaultValue<T>::ValueProducer* DefaultValue<T>::producer_ = nullptr;

// Points to the user-set default value for type T&.
template <typename T>
T* DefaultValue<T&>::address_ = nullptr;

// Implement this interface to define an action for function type F.
template <typename F>
class ActionInterface {
 public:
  typedef typename internal::Function<F>::Result Result;
  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;

  ActionInterface() {}
  virtual ~ActionInterface() {}

  // Performs the action.  This method is not const, as in general an
  // action can have side effects and be stateful.  For example, a
  // get-the-next-element-from-the-collection action will need to
  // remember the current element.
  virtual Result Perform(const ArgumentTuple& args) = 0;

 private:
  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionInterface);
};

// An Action<F> is a copyable and IMMUTABLE (except by assignment)
// object that represents an action to be taken when a mock function
// of type F is called.  The implementation of Action<T> is just a
// std::shared_ptr to const ActionInterface<T>. Don't inherit from Action!
// You can view an object implementing ActionInterface<F> as a
// concrete action (including its current state), and an Action<F>
// object as a handle to it.
template <typename F>
class Action {
  // Adapter class to allow constructing Action from a legacy ActionInterface.
  // New code should create Actions from functors instead.
  struct ActionAdapter {
    // Adapter must be copyable to satisfy std::function requirements.
    ::std::shared_ptr<ActionInterface<F>> impl_;

    template <typename... Args>
    typename internal::Function<F>::Result operator()(Args&&... args) {
      return impl_->Perform(
          ::std::forward_as_tuple(::std::forward<Args>(args)...));
    }
  };

  template <typename G>
  using IsCompatibleFunctor = std::is_constructible<std::function<F>, G>;

 public:
  typedef typename internal::Function<F>::Result Result;
  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;

  // Constructs a null Action.  Needed for storing Action objects in
  // STL containers.
  Action() {}

  // Construct an Action from a specified callable.
  // This cannot take std::function directly, because then Action would not be
  // directly constructible from lambda (it would require two conversions).
  template <
      typename G,
      typename = typename std::enable_if<internal::disjunction<
          IsCompatibleFunctor<G>, std::is_constructible<std::function<Result()>,
                                                        G>>::value>::type>
  Action(G&& fun) {  // NOLINT
    Init(::std::forward<G>(fun), IsCompatibleFunctor<G>());
  }

  // Constructs an Action from its implementation.
  explicit Action(ActionInterface<F>* impl)
      : fun_(ActionAdapter{::std::shared_ptr<ActionInterface<F>>(impl)}) {}

  // This constructor allows us to turn an Action<Func> object into an
  // Action<F>, as long as F's arguments can be implicitly converted
  // to Func's and Func's return type can be implicitly converted to F's.
  template <typename Func>
  explicit Action(const Action<Func>& action) : fun_(action.fun_) {}

  // Returns true if and only if this is the DoDefault() action.
  bool IsDoDefault() const { return fun_ == nullptr; }

  // Performs the action.  Note that this method is const even though
  // the corresponding method in ActionInterface is not.  The reason
  // is that a const Action<F> means that it cannot be re-bound to
  // another concrete action, not that the concrete action it binds to
  // cannot change state.  (Think of the difference between a const
  // pointer and a pointer to const.)
  Result Perform(ArgumentTuple args) const {
    if (IsDoDefault()) {
      internal::IllegalDoDefault(__FILE__, __LINE__);
    }
    return internal::Apply(fun_, ::std::move(args));
  }

 private:
  template <typename G>
  friend class Action;

  template <typename G>
  void Init(G&& g, ::std::true_type) {
    fun_ = ::std::forward<G>(g);
  }

  template <typename G>
  void Init(G&& g, ::std::false_type) {
    fun_ = IgnoreArgs<typename ::std::decay<G>::type>{::std::forward<G>(g)};
  }

  template <typename FunctionImpl>
  struct IgnoreArgs {
    template <typename... Args>
    Result operator()(const Args&...) const {
      return function_impl();
    }

    FunctionImpl function_impl;
  };

  // fun_ is an empty function if and only if this is the DoDefault() action.
  ::std::function<F> fun_;
};

// The PolymorphicAction class template makes it easy to implement a
// polymorphic action (i.e. an action that can be used in mock
// functions of than one type, e.g. Return()).
//
// To define a polymorphic action, a user first provides a COPYABLE
// implementation class that has a Perform() method template:
//
//   class FooAction {
//    public:
//     template <typename Result, typename ArgumentTuple>
//     Result Perform(const ArgumentTuple& args) const {
//       // Processes the arguments and returns a result, using
//       // std::get<N>(args) to get the N-th (0-based) argument in the tuple.
//     }
//     ...
//   };
//
// Then the user creates the polymorphic action using
// MakePolymorphicAction(object) where object has type FooAction.  See
// the definition of Return(void) and SetArgumentPointee<N>(value) for
// complete examples.
template <typename Impl>
class PolymorphicAction {
 public:
  explicit PolymorphicAction(const Impl& impl) : impl_(impl) {}

  template <typename F>
  operator Action<F>() const {
    return Action<F>(new MonomorphicImpl<F>(impl_));
  }

 private:
  template <typename F>
  class MonomorphicImpl : public ActionInterface<F> {
   public:
    typedef typename internal::Function<F>::Result Result;
    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;

    explicit MonomorphicImpl(const Impl& impl) : impl_(impl) {}

    Result Perform(const ArgumentTuple& args) override {
      return impl_.template Perform<Result>(args);
    }

   private:
    Impl impl_;
  };

  Impl impl_;
};

// Creates an Action from its implementation and returns it.  The
// created Action object owns the implementation.
template <typename F>
Action<F> MakeAction(ActionInterface<F>* impl) {
  return Action<F>(impl);
}

// Creates a polymorphic action from its implementation.  This is
// easier to use than the PolymorphicAction<Impl> constructor as it
// doesn't require you to explicitly write the template argument, e.g.
//
//   MakePolymorphicAction(foo);
// vs
//   PolymorphicAction<TypeOfFoo>(foo);
template <typename Impl>
inline PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl) {
  return PolymorphicAction<Impl>(impl);
}

namespace internal {

template <typename F>
class TypedExpectation;

// Specialized for function types below.
template <typename F>
class OnceAction;

// An action that can only be used once.
//
// This is what is accepted by WillOnce, which doesn't require the underlying
// action to be copy-constructible (only move-constructible), and promises to
// invoke it as an rvalue reference. This allows the action to work with
// move-only types like std::move_only_function in a type-safe manner.
//
// For example:
//
//     // Assume we have some API that needs to accept a unique pointer to some
//     // non-copyable object Foo.
//     void AcceptUniquePointer(std::unique_ptr<Foo> foo);
//
//     // We can define an action that provides a Foo to that API. Because It
//     // has to give away its unique pointer, it must not be called more than
//     // once, so its call operator is &&-qualified.
//     struct ProvideFoo {
//       std::unique_ptr<Foo> foo;
//
//       void operator()() && {
//         AcceptUniquePointer(std::move(Foo));
//       }
//     };
//
//     // This action can be used with WillOnce.
//     EXPECT_CALL(mock, Call)
//         .WillOnce(ProvideFoo{std::make_unique<Foo>(...)});
//
//     // But a call to WillRepeatedly will fail to compile. This is correct,
//     // since the action cannot correctly be used repeatedly.
//     EXPECT_CALL(mock, Call)
//         .WillRepeatedly(ProvideFoo{std::make_unique<Foo>(...)});
//
// A less-contrived example would be an action that returns an arbitrary type,
// whose &&-qualified call operator is capable of dealing with move-only types.
template <typename Result, typename... Args>
class OnceAction<Result(Args...)> final {
 private:
  // True iff we can use the given callable type (or lvalue reference) directly
  // via ActionAdaptor.
  template <typename Callable>
  using IsDirectlyCompatible = internal::conjunction<
      // It must be possible to capture the callable in ActionAdaptor.
      std::is_constructible<typename std::decay<Callable>::type, Callable>,
      // The callable must be compatible with our signature.
      internal::is_callable_r<Result, typename std::decay<Callable>::type,
                              Args...>>;

  // True iff we can use the given callable type via ActionAdaptor once we
  // ignore incoming arguments.
  template <typename Callable>
  using IsCompatibleAfterIgnoringArguments = internal::conjunction<
      // It must be possible to capture the callable in a lambda.
      std::is_constructible<typename std::decay<Callable>::type, Callable>,
      // The callable must be invocable with zero arguments, returning something
      // convertible to Result.
      internal::is_callable_r<Result, typename std::decay<Callable>::type>>;

 public:
  // Construct from a callable that is directly compatible with our mocked
  // signature: it accepts our function type's arguments and returns something
  // convertible to our result type.
  template <typename Callable,
            typename std::enable_if<
                internal::conjunction<
                    // Teach clang on macOS that we're not talking about a
                    // copy/move constructor here. Otherwise it gets confused
                    // when checking the is_constructible requirement of our
                    // traits above.
                    internal::negation<std::is_same<
                        OnceAction, typename std::decay<Callable>::type>>,
                    IsDirectlyCompatible<Callable>>  //
                ::value,
                int>::type = 0>
  OnceAction(Callable&& callable)  // NOLINT
      : action_(ActionAdaptor<typename std::decay<Callable>::type>(
            {}, std::forward<Callable>(callable))) {}

  // As above, but for a callable that ignores the mocked function's arguments.
  template <typename Callable,
            typename std::enable_if<
                internal::conjunction<
                    // Teach clang on macOS that we're not talking about a
                    // copy/move constructor here. Otherwise it gets confused
                    // when checking the is_constructible requirement of our
                    // traits above.
                    internal::negation<std::is_same<
                        OnceAction, typename std::decay<Callable>::type>>,
                    // Exclude callables for which the overload above works.
                    // We'd rather provide the arguments if possible.
                    internal::negation<IsDirectlyCompatible<Callable>>,
                    IsCompatibleAfterIgnoringArguments<Callable>>::value,
                int>::type = 0>
  OnceAction(Callable&& callable)  // NOLINT
                                   // Call the constructor above with a callable
                                   // that ignores the input arguments.
      : OnceAction(IgnoreIncomingArguments<typename std::decay<Callable>::type>{
            std::forward<Callable>(callable)}) {}

  // A fallback constructor for anything that is convertible to Action, for use
  // with legacy actions that uses older styles like implementing
  // ActionInterface or a conversion operator to Action. Modern code should
  // implement a call operator with appropriate restrictions.
  template <typename T,
            typename std::enable_if<
                internal::conjunction<
                    // Teach clang on macOS that we're not talking about a
                    // copy/move constructor here. Otherwise it gets confused
                    // when checking the is_constructible requirement of our
                    // traits above.
                    internal::negation<
                        std::is_same<OnceAction, typename std::decay<T>::type>>,
                    // Exclude the overloads above, which we want to take
                    // precedence.
                    internal::negation<IsDirectlyCompatible<T>>,
                    internal::negation<IsCompatibleAfterIgnoringArguments<T>>,
                    // It must be possible to turn the object into an action of
                    // the appropriate type.
                    std::is_convertible<T, Action<Result(Args...)>>  //
                    >::value,
                int>::type = 0>
  OnceAction(T&& action) : action_(std::forward<T>(action)) {}  // NOLINT

  // We are naturally copyable because we store only an Action, but semantically
  // we should not be copyable.
  OnceAction(const OnceAction&) = delete;
  OnceAction& operator=(const OnceAction&) = delete;
  OnceAction(OnceAction&&) = default;

 private:
  // Allow TypedExpectation::WillOnce to use our type-unsafe API below.
  friend class TypedExpectation<Result(Args...)>;

  // An adaptor that wraps a callable that is compatible with our signature and
  // being invoked as an rvalue reference so that it can be used as an
  // Action. This throws away type safety, but that's fine because this is only
  // used by WillOnce, which we know calls at most once.
  template <typename Callable>
  class ActionAdaptor final {
   public:
    // A tag indicating that the (otherwise universal) constructor is accepting
    // the callable itself, instead of e.g. stealing calls for the move
    // constructor.
    struct CallableTag final {};

    template <typename F>
    explicit ActionAdaptor(CallableTag, F&& callable)
        : callable_(std::make_shared<Callable>(std::forward<F>(callable))) {}

    // Rather than explicitly returning Result, we return whatever the wrapped
    // callable returns. This allows for compatibility with existing uses like
    // the following, when the mocked function returns void:
    //
    //     EXPECT_CALL(mock_fn_, Call)
    //         .WillOnce([&] {
    //            [...]
    //            return 0;
    //         });
    //
    // This works with Action since such a callable can be turned into
    // std::function<void()>. If we use an explicit return type of Result here
    // then it *doesn't* work with OnceAction, because we'll get a "void
    // function should not return a value" error.
    //
    // We need not worry about incompatible result types because the SFINAE on
    // OnceAction already checks this for us. std::is_invocable_r_v itself makes
    // the same allowance for void result types.
    template <typename... ArgRefs>
    internal::call_result_t<Callable, ArgRefs...> operator()(
        ArgRefs&&... args) const {
      return std::move(*callable_)(std::forward<ArgRefs>(args)...);
    }

   private:
    // We must put the callable on the heap so that we are copyable, which
    // Action needs.
    std::shared_ptr<Callable> callable_;
  };

  // An adaptor that makes a callable that accepts zero arguments callable with
  // our mocked arguments.
  template <typename Callable>
  struct IgnoreIncomingArguments {
    internal::call_result_t<Callable> operator()(Args&&...) {
      return std::move(callable)();
    }

    Callable callable;
  };

  // Return an Action that calls the underlying callable in a type-safe manner.
  // The action's Perform method must be called at most once.
  //
  // This is the transition from a type-safe API to a type-unsafe one, since
  // "must be called at most once" is no longer reflecting in the type system.
  Action<Result(Args...)> ReleaseAction() && { return std::move(action_); }

  Action<Result(Args...)> action_;
};

// Helper struct to specialize ReturnAction to execute a move instead of a copy
// on return. Useful for move-only types, but could be used on any type.
template <typename T>
struct ByMoveWrapper {
  explicit ByMoveWrapper(T value) : payload(std::move(value)) {}
  T payload;
};

// Implements the polymorphic Return(x) action, which can be used in
// any function that returns the type of x, regardless of the argument
// types.
//
// Note: The value passed into Return must be converted into
// Function<F>::Result when this action is cast to Action<F> rather than
// when that action is performed. This is important in scenarios like
//
// MOCK_METHOD1(Method, T(U));
// ...
// {
//   Foo foo;
//   X x(&foo);
//   EXPECT_CALL(mock, Method(_)).WillOnce(Return(x));
// }
//
// In the example above the variable x holds reference to foo which leaves
// scope and gets destroyed.  If copying X just copies a reference to foo,
// that copy will be left with a hanging reference.  If conversion to T
// makes a copy of foo, the above code is safe. To support that scenario, we
// need to make sure that the type conversion happens inside the EXPECT_CALL
// statement, and conversion of the result of Return to Action<T(U)> is a
// good place for that.
//
// The real life example of the above scenario happens when an invocation
// of gtl::Container() is passed into Return.
//
template <typename R>
class ReturnAction {
 public:
  // Constructs a ReturnAction object from the value to be returned.
  // 'value' is passed by value instead of by const reference in order
  // to allow Return("string literal") to compile.
  explicit ReturnAction(R value) : value_(new R(std::move(value))) {}

  // This template type conversion operator allows Return(x) to be
  // used in ANY function that returns x's type.
  template <typename F>
  operator Action<F>() const {  // NOLINT
    // Assert statement belongs here because this is the best place to verify
    // conditions on F. It produces the clearest error messages
    // in most compilers.
    // Impl really belongs in this scope as a local class but can't
    // because MSVC produces duplicate symbols in different translation units
    // in this case. Until MS fixes that bug we put Impl into the class scope
    // and put the typedef both here (for use in assert statement) and
    // in the Impl class. But both definitions must be the same.
    typedef typename Function<F>::Result Result;
    static_assert(!std::is_reference<Result>::value,
                  "use ReturnRef instead of Return to return a reference");
    static_assert(!std::is_void<Result>::value,
                  "Can't use Return() on an action expected to return `void`.");
    return Action<F>(new Impl<R, F>(value_));
  }

 private:
  // Implements the Return(x) action for a particular function type F.
  template <typename R_, typename F>
  class Impl : public ActionInterface<F> {
   public:
    typedef typename Function<F>::Result Result;
    typedef typename Function<F>::ArgumentTuple ArgumentTuple;

    // The implicit cast is necessary when Result has more than one
    // single-argument constructor (e.g. Result is std::vector<int>) and R
    // has a type conversion operator template.  In that case, value_(value)
    // won't compile as the compiler doesn't known which constructor of
    // Result to call.  ImplicitCast_ forces the compiler to convert R to
    // Result without considering explicit constructors, thus resolving the
    // ambiguity. value_ is then initialized using its copy constructor.
    explicit Impl(const std::shared_ptr<R>& value)
        : value_before_cast_(*value),
          value_(ImplicitCast_<Result>(value_before_cast_)) {}

    Result Perform(const ArgumentTuple&) override { return value_; }

   private:
    static_assert(!std::is_reference<Result>::value,
                  "Result cannot be a reference type");
    // We save the value before casting just in case it is being cast to a
    // wrapper type.
    R value_before_cast_;
    Result value_;

    GTEST_DISALLOW_COPY_AND_ASSIGN_(Impl);
  };

  // Partially specialize for ByMoveWrapper. This version of ReturnAction will
  // move its contents instead.
  template <typename R_, typename F>
  class Impl<ByMoveWrapper<R_>, F> : public ActionInterface<F> {
   public:
    typedef typename Function<F>::Result Result;
    typedef typename Function<F>::ArgumentTuple ArgumentTuple;

    explicit Impl(const std::shared_ptr<R>& wrapper)
        : performed_(false), wrapper_(wrapper) {}

    Result Perform(const ArgumentTuple&) override {
      GTEST_CHECK_(!performed_)
          << "A ByMove() action should only be performed once.";
      performed_ = true;
      return std::move(wrapper_->payload);
    }

   private:
    bool performed_;
    const std::shared_ptr<R> wrapper_;
  };

  const std::shared_ptr<R> value_;
};

// Implements the ReturnNull() action.
class ReturnNullAction {
 public:
  // Allows ReturnNull() to be used in any pointer-returning function. In C++11
  // this is enforced by returning nullptr, and in non-C++11 by asserting a
  // pointer type on compile time.
  template <typename Result, typename ArgumentTuple>
  static Result Perform(const ArgumentTuple&) {
    return nullptr;
  }
};

// Implements the Return() action.
class ReturnVoidAction {
 public:
  // Allows Return() to be used in any void-returning function.
  template <typename Result, typename ArgumentTuple>
  static void Perform(const ArgumentTuple&) {
    static_assert(std::is_void<Result>::value, "Result should be void.");
  }
};

// Implements the polymorphic ReturnRef(x) action, which can be used
// in any function that returns a reference to the type of x,
// regardless of the argument types.
template <typename T>
class ReturnRefAction {
 public:
  // Constructs a ReturnRefAction object from the reference to be returned.
  explicit ReturnRefAction(T& ref) : ref_(ref) {}  // NOLINT

  // This template type conversion operator allows ReturnRef(x) to be
  // used in ANY function that returns a reference to x's type.
  template <typename F>
  operator Action<F>() const {
    typedef typename Function<F>::Result Result;
    // Asserts that the function return type is a reference.  This
    // catches the user error of using ReturnRef(x) when Return(x)
    // should be used, and generates some helpful error message.
    static_assert(std::is_reference<Result>::value,
                  "use Return instead of ReturnRef to return a value");
    return Action<F>(new Impl<F>(ref_));
  }

 private:
  // Implements the ReturnRef(x) action for a particular function type F.
  template <typename F>
  class Impl : public ActionInterface<F> {
   public:
    typedef typename Function<F>::Result Result;
    typedef typename Function<F>::ArgumentTuple ArgumentTuple;

    explicit Impl(T& ref) : ref_(ref) {}  // NOLINT

    Result Perform(const ArgumentTuple&) override { return ref_; }

   private:
    T& ref_;
  };

  T& ref_;
};

// Implements the polymorphic ReturnRefOfCopy(x) action, which can be
// used in any function that returns a reference to the type of x,
// regardless of the argument types.
template <typename T>
class ReturnRefOfCopyAction {
 public:
  // Constructs a ReturnRefOfCopyAction object from the reference to
  // be returned.
  explicit ReturnRefOfCopyAction(const T& value) : value_(value) {}  // NOLINT

  // This template type conversion operator allows ReturnRefOfCopy(x) to be
  // used in ANY function that returns a reference to x's type.
  template <typename F>
  operator Action<F>() const {
    typedef typename Function<F>::Result Result;
    // Asserts that the function return type is a reference.  This
    // catches the user error of using ReturnRefOfCopy(x) when Return(x)
    // should be used, and generates some helpful error message.
    static_assert(std::is_reference<Result>::value,
                  "use Return instead of ReturnRefOfCopy to return a value");
    return Action<F>(new Impl<F>(value_));
  }

 private:
  // Implements the ReturnRefOfCopy(x) action for a particular function type F.
  template <typename F>
  class Impl : public ActionInterface<F> {
   public:
    typedef typename Function<F>::Result Result;
    typedef typename Function<F>::ArgumentTuple ArgumentTuple;

    explicit Impl(const T& value) : value_(value) {}  // NOLINT

    Result Perform(const ArgumentTuple&) override { return value_; }

   private:
    T value_;
  };

  const T value_;
};

// Implements the polymorphic ReturnRoundRobin(v) action, which can be
// used in any function that returns the element_type of v.
template <typename T>
class ReturnRoundRobinAction {
 public:
  explicit ReturnRoundRobinAction(std::vector<T> values) {
    GTEST_CHECK_(!values.empty())
        << "ReturnRoundRobin requires at least one element.";
    state_->values = std::move(values);
  }

  template <typename... Args>
  T operator()(Args&&...) const {
    return state_->Next();
  }

 private:
  struct State {
    T Next() {
      T ret_val = values[i++];
      if (i == values.size()) i = 0;
      return ret_val;
    }

    std::vector<T> values;
    size_t i = 0;
  };
  std::shared_ptr<State> state_ = std::make_shared<State>();
};

// Implements the polymorphic DoDefault() action.
class DoDefaultAction {
 public:
  // This template type conversion operator allows DoDefault() to be
  // used in any function.
  template <typename F>
  operator Action<F>() const {
    return Action<F>();
  }  // NOLINT
};

// Implements the Assign action to set a given pointer referent to a
// particular value.
template <typename T1, typename T2>
class AssignAction {
 public:
  AssignAction(T1* ptr, T2 value) : ptr_(ptr), value_(value) {}

  template <typename Result, typename ArgumentTuple>
  void Perform(const ArgumentTuple& /* args */) const {
    *ptr_ = value_;
  }

 private:
  T1* const ptr_;
  const T2 value_;
};

#if !GTEST_OS_WINDOWS_MOBILE

// Implements the SetErrnoAndReturn action to simulate return from
// various system calls and libc functions.
template <typename T>
class SetErrnoAndReturnAction {
 public:
  SetErrnoAndReturnAction(int errno_value, T result)
      : errno_(errno_value), result_(result) {}
  template <typename Result, typename ArgumentTuple>
  Result Perform(const ArgumentTuple& /* args */) const {
    errno = errno_;
    return result_;
  }

 private:
  const int errno_;
  const T result_;
};

#endif  // !GTEST_OS_WINDOWS_MOBILE

// Implements the SetArgumentPointee<N>(x) action for any function
// whose N-th argument (0-based) is a pointer to x's type.
template <size_t N, typename A, typename = void>
struct SetArgumentPointeeAction {
  A value;

  template <typename... Args>
  void operator()(const Args&... args) const {
    *::std::get<N>(std::tie(args...)) = value;
  }
};

// Implements the Invoke(object_ptr, &Class::Method) action.
template <class Class, typename MethodPtr>
struct InvokeMethodAction {
  Class* const obj_ptr;
  const MethodPtr method_ptr;

  template <typename... Args>
  auto operator()(Args&&... args) const
      -> decltype((obj_ptr->*method_ptr)(std::forward<Args>(args)...)) {
    return (obj_ptr->*method_ptr)(std::forward<Args>(args)...);
  }
};

// Implements the InvokeWithoutArgs(f) action.  The template argument
// FunctionImpl is the implementation type of f, which can be either a
// function pointer or a functor.  InvokeWithoutArgs(f) can be used as an
// Action<F> as long as f's type is compatible with F.
template <typename FunctionImpl>
struct InvokeWithoutArgsAction {
  FunctionImpl function_impl;

  // Allows InvokeWithoutArgs(f) to be used as any action whose type is
  // compatible with f.
  template <typename... Args>
  auto operator()(const Args&...) -> decltype(function_impl()) {
    return function_impl();
  }
};

// Implements the InvokeWithoutArgs(object_ptr, &Class::Method) action.
template <class Class, typename MethodPtr>
struct InvokeMethodWithoutArgsAction {
  Class* const obj_ptr;
  const MethodPtr method_ptr;

  using ReturnType =
      decltype((std::declval<Class*>()->*std::declval<MethodPtr>())());

  template <typename... Args>
  ReturnType operator()(const Args&...) const {
    return (obj_ptr->*method_ptr)();
  }
};

// Implements the IgnoreResult(action) action.
template <typename A>
class IgnoreResultAction {
 public:
  explicit IgnoreResultAction(const A& action) : action_(action) {}

  template <typename F>
  operator Action<F>() const {
    // Assert statement belongs here because this is the best place to verify
    // conditions on F. It produces the clearest error messages
    // in most compilers.
    // Impl really belongs in this scope as a local class but can't
    // because MSVC produces duplicate symbols in different translation units
    // in this case. Until MS fixes that bug we put Impl into the class scope
    // and put the typedef both here (for use in assert statement) and
    // in the Impl class. But both definitions must be the same.
    typedef typename internal::Function<F>::Result Result;

    // Asserts at compile time that F returns void.
    static_assert(std::is_void<Result>::value, "Result type should be void.");

    return Action<F>(new Impl<F>(action_));
  }

 private:
  template <typename F>
  class Impl : public ActionInterface<F> {
   public:
    typedef typename internal::Function<F>::Result Result;
    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;

    explicit Impl(const A& action) : action_(action) {}

    void Perform(const ArgumentTuple& args) override {
      // Performs the action and ignores its result.
      action_.Perform(args);
    }

   private:
    // Type OriginalFunction is the same as F except that its return
    // type is IgnoredValue.
    typedef
        typename internal::Function<F>::MakeResultIgnoredValue OriginalFunction;

    const Action<OriginalFunction> action_;
  };

  const A action_;
};

template <typename InnerAction, size_t... I>
struct WithArgsAction {
  InnerAction action;

  // The inner action could be anything convertible to Action<X>.
  // We use the conversion operator to detect the signature of the inner Action.
  template <typename R, typename... Args>
  operator Action<R(Args...)>() const {  // NOLINT
    using TupleType = std::tuple<Args...>;
    Action<R(typename std::tuple_element<I, TupleType>::type...)> converted(
        action);

    return [converted](Args... args) -> R {
      return converted.Perform(std::forward_as_tuple(
          std::get<I>(std::forward_as_tuple(std::forward<Args>(args)...))...));
    };
  }
};

template <typename... Actions>
struct DoAllAction {
 private:
  // The type of reference that should be provided to an initial action for a
  // mocked function parameter of type T.
  //
  // There are two quirks here:
  //
  //  *  Unlike most forwarding functions, we pass scalars through by value.
  //     This isn't strictly necessary because an lvalue reference would work
  //     fine too and be consistent with other non-reference types, but it's
  //     perhaps less surprising.
  //
  //     For example if the mocked function has signature void(int), then it
  //     might seem surprising for the user's initial action to need to be
  //     convertible to Action<void(const int&)>. This is perhaps less
  //     surprising for a non-scalar type where there may be a performance
  //     impact, or it might even be impossible, to pass by value.
  //
  //  *  More surprisingly, `const T&` is often not a const reference type.
  //     By the reference collapsing rules in C++17 [dcl.ref]/6, if T refers to
  //     U& or U&& for some non-scalar type U, then NonFinalType<T> is U&. In
  //     other words, we may hand over a non-const reference.
  //
  //     So for example, given some non-scalar type Obj we have the following
  //     mappings:
  //
  //            T               NonFinalType<T>
  //         -------            ---------------
  //         Obj                const Obj&
  //         Obj&               Obj&
  //         Obj&&              Obj&
  //         const Obj          const Obj&
  //         const Obj&         const Obj&
  //         const Obj&&        const Obj&
  //
  //     In other words, the initial actions get a mutable view of an non-scalar
  //     argument if and only if the mock function itself accepts a non-const
  //     reference type. They are never given an rvalue reference to an
  //     non-scalar type.
  //
  //     This situation makes sense if you imagine use with a matcher that is
  //     designed to write through a reference. For example, if the caller wants
  //     to fill in a reference argument and then return a canned value:
  //
  //         EXPECT_CALL(mock, Call)
  //             .WillOnce(DoAll(SetArgReferee<0>(17), Return(19)));
  //
  template <typename T>
  using NonFinalType =
      typename std::conditional<std::is_scalar<T>::value, T, const T&>::type;

  template <typename ActionT, size_t... I>
  std::vector<ActionT> Convert(IndexSequence<I...>) const {
    return {ActionT(std::get<I>(actions))...};
  }

 public:
  std::tuple<Actions...> actions;

  template <typename R, typename... Args>
  operator Action<R(Args...)>() const {  // NOLINT
    struct Op {
      std::vector<Action<void(NonFinalType<Args>...)>> converted;
      Action<R(Args...)> last;
      R operator()(Args... args) const {
        auto tuple_args = std::forward_as_tuple(std::forward<Args>(args)...);
        for (auto& a : converted) {
          a.Perform(tuple_args);
        }
        return last.Perform(std::move(tuple_args));
      }
    };
    return Op{Convert<Action<void(NonFinalType<Args>...)>>(
                  MakeIndexSequence<sizeof...(Actions) - 1>()),
              std::get<sizeof...(Actions) - 1>(actions)};
  }
};

template <typename T, typename... Params>
struct ReturnNewAction {
  T* operator()() const {
    return internal::Apply(
        [](const Params&... unpacked_params) {
          return new T(unpacked_params...);
        },
        params);
  }
  std::tuple<Params...> params;
};

template <size_t k>
struct ReturnArgAction {
  template <typename... Args,
            typename = typename std::enable_if<(k < sizeof...(Args))>::type>
  auto operator()(Args&&... args) const -> decltype(std::get<k>(
      std::forward_as_tuple(std::forward<Args>(args)...))) {
    return std::get<k>(std::forward_as_tuple(std::forward<Args>(args)...));
  }
};

template <size_t k, typename Ptr>
struct SaveArgAction {
  Ptr pointer;

  template <typename... Args>
  void operator()(const Args&... args) const {
    *pointer = std::get<k>(std::tie(args...));
  }
};

template <size_t k, typename Ptr>
struct SaveArgPointeeAction {
  Ptr pointer;

  template <typename... Args>
  void operator()(const Args&... args) const {
    *pointer = *std::get<k>(std::tie(args...));
  }
};

template <size_t k, typename T>
struct SetArgRefereeAction {
  T value;

  template <typename... Args>
  void operator()(Args&&... args) const {
    using argk_type =
        typename ::std::tuple_element<k, std::tuple<Args...>>::type;
    static_assert(std::is_lvalue_reference<argk_type>::value,
                  "Argument must be a reference type.");
    std::get<k>(std::tie(args...)) = value;
  }
};

template <size_t k, typename I1, typename I2>
struct SetArrayArgumentAction {
  I1 first;
  I2 last;

  template <typename... Args>
  void operator()(const Args&... args) const {
    auto value = std::get<k>(std::tie(args...));
    for (auto it = first; it != last; ++it, (void)++value) {
      *value = *it;
    }
  }
};

template <size_t k>
struct DeleteArgAction {
  template <typename... Args>
  void operator()(const Args&... args) const {
    delete std::get<k>(std::tie(args...));
  }
};

template <typename Ptr>
struct ReturnPointeeAction {
  Ptr pointer;
  template <typename... Args>
  auto operator()(const Args&...) const -> decltype(*pointer) {
    return *pointer;
  }
};

#if GTEST_HAS_EXCEPTIONS
template <typename T>
struct ThrowAction {
  T exception;
  // We use a conversion operator to adapt to any return type.
  template <typename R, typename... Args>
  operator Action<R(Args...)>() const {  // NOLINT
    T copy = exception;
    return [copy](Args...) -> R { throw copy; };
  }
};
#endif  // GTEST_HAS_EXCEPTIONS

}  // namespace internal

// An Unused object can be implicitly constructed from ANY value.
// This is handy when defining actions that ignore some or all of the
// mock function arguments.  For example, given
//
//   MOCK_METHOD3(Foo, double(const string& label, double x, double y));
//   MOCK_METHOD3(Bar, double(int index, double x, double y));
//
// instead of
//
//   double DistanceToOriginWithLabel(const string& label, double x, double y) {
//     return sqrt(x*x + y*y);
//   }
//   double DistanceToOriginWithIndex(int index, double x, double y) {
//     return sqrt(x*x + y*y);
//   }
//   ...
//   EXPECT_CALL(mock, Foo("abc", _, _))
//       .WillOnce(Invoke(DistanceToOriginWithLabel));
//   EXPECT_CALL(mock, Bar(5, _, _))
//       .WillOnce(Invoke(DistanceToOriginWithIndex));
//
// you could write
//
//   // We can declare any uninteresting argument as Unused.
//   double DistanceToOrigin(Unused, double x, double y) {
//     return sqrt(x*x + y*y);
//   }
//   ...
//   EXPECT_CALL(mock, Foo("abc", _, _)).WillOnce(Invoke(DistanceToOrigin));
//   EXPECT_CALL(mock, Bar(5, _, _)).WillOnce(Invoke(DistanceToOrigin));
typedef internal::IgnoredValue Unused;

// Creates an action that does actions a1, a2, ..., sequentially in
// each invocation. All but the last action will have a readonly view of the
// arguments.
template <typename... Action>
internal::DoAllAction<typename std::decay<Action>::type...> DoAll(
    Action&&... action) {
  return {std::forward_as_tuple(std::forward<Action>(action)...)};
}

// WithArg<k>(an_action) creates an action that passes the k-th
// (0-based) argument of the mock function to an_action and performs
// it.  It adapts an action accepting one argument to one that accepts
// multiple arguments.  For convenience, we also provide
// WithArgs<k>(an_action) (defined below) as a synonym.
template <size_t k, typename InnerAction>
internal::WithArgsAction<typename std::decay<InnerAction>::type, k> WithArg(
    InnerAction&& action) {
  return {std::forward<InnerAction>(action)};
}

// WithArgs<N1, N2, ..., Nk>(an_action) creates an action that passes
// the selected arguments of the mock function to an_action and
// performs it.  It serves as an adaptor between actions with
// different argument lists.
template <size_t k, size_t... ks, typename InnerAction>
internal::WithArgsAction<typename std::decay<InnerAction>::type, k, ks...>
WithArgs(InnerAction&& action) {
  return {std::forward<InnerAction>(action)};
}

// WithoutArgs(inner_action) can be used in a mock function with a
// non-empty argument list to perform inner_action, which takes no
// argument.  In other words, it adapts an action accepting no
// argument to one that accepts (and ignores) arguments.
template <typename InnerAction>
internal::WithArgsAction<typename std::decay<InnerAction>::type> WithoutArgs(
    InnerAction&& action) {
  return {std::forward<InnerAction>(action)};
}

// Creates an action that returns 'value'.  'value' is passed by value
// instead of const reference - otherwise Return("string literal")
// will trigger a compiler error about using array as initializer.
template <typename R>
internal::ReturnAction<R> Return(R value) {
  return internal::ReturnAction<R>(std::move(value));
}

// Creates an action that returns NULL.
inline PolymorphicAction<internal::ReturnNullAction> ReturnNull() {
  return MakePolymorphicAction(internal::ReturnNullAction());
}

// Creates an action that returns from a void function.
inline PolymorphicAction<internal::ReturnVoidAction> Return() {
  return MakePolymorphicAction(internal::ReturnVoidAction());
}

// Creates an action that returns the reference to a variable.
template <typename R>
inline internal::ReturnRefAction<R> ReturnRef(R& x) {  // NOLINT
  return internal::ReturnRefAction<R>(x);
}

// Prevent using ReturnRef on reference to temporary.
template <typename R, R* = nullptr>
internal::ReturnRefAction<R> ReturnRef(R&&) = delete;

// Creates an action that returns the reference to a copy of the
// argument.  The copy is created when the action is constructed and
// lives as long as the action.
template <typename R>
inline internal::ReturnRefOfCopyAction<R> ReturnRefOfCopy(const R& x) {
  return internal::ReturnRefOfCopyAction<R>(x);
}

// Modifies the parent action (a Return() action) to perform a move of the
// argument instead of a copy.
// Return(ByMove()) actions can only be executed once and will assert this
// invariant.
template <typename R>
internal::ByMoveWrapper<R> ByMove(R x) {
  return internal::ByMoveWrapper<R>(std::move(x));
}

// Creates an action that returns an element of `vals`. Calling this action will
// repeatedly return the next value from `vals` until it reaches the end and
// will restart from the beginning.
template <typename T>
internal::ReturnRoundRobinAction<T> ReturnRoundRobin(std::vector<T> vals) {
  return internal::ReturnRoundRobinAction<T>(std::move(vals));
}

// Creates an action that returns an element of `vals`. Calling this action will
// repeatedly return the next value from `vals` until it reaches the end and
// will restart from the beginning.
template <typename T>
internal::ReturnRoundRobinAction<T> ReturnRoundRobin(
    std::initializer_list<T> vals) {
  return internal::ReturnRoundRobinAction<T>(std::vector<T>(vals));
}

// Creates an action that does the default action for the give mock function.
inline internal::DoDefaultAction DoDefault() {
  return internal::DoDefaultAction();
}

// Creates an action that sets the variable pointed by the N-th
// (0-based) function argument to 'value'.
template <size_t N, typename T>
internal::SetArgumentPointeeAction<N, T> SetArgPointee(T value) {
  return {std::move(value)};
}

// The following version is DEPRECATED.
template <size_t N, typename T>
internal::SetArgumentPointeeAction<N, T> SetArgumentPointee(T value) {
  return {std::move(value)};
}

// Creates an action that sets a pointer referent to a given value.
template <typename T1, typename T2>
PolymorphicAction<internal::AssignAction<T1, T2>> Assign(T1* ptr, T2 val) {
  return MakePolymorphicAction(internal::AssignAction<T1, T2>(ptr, val));
}

#if !GTEST_OS_WINDOWS_MOBILE

// Creates an action that sets errno and returns the appropriate error.
template <typename T>
PolymorphicAction<internal::SetErrnoAndReturnAction<T>> SetErrnoAndReturn(
    int errval, T result) {
  return MakePolymorphicAction(
      internal::SetErrnoAndReturnAction<T>(errval, result));
}

#endif  // !GTEST_OS_WINDOWS_MOBILE

// Various overloads for Invoke().

// Legacy function.
// Actions can now be implicitly constructed from callables. No need to create
// wrapper objects.
// This function exists for backwards compatibility.
template <typename FunctionImpl>
typename std::decay<FunctionImpl>::type Invoke(FunctionImpl&& function_impl) {
  return std::forward<FunctionImpl>(function_impl);
}

// Creates an action that invokes the given method on the given object
// with the mock function's arguments.
template <class Class, typename MethodPtr>
internal::InvokeMethodAction<Class, MethodPtr> Invoke(Class* obj_ptr,
                                                      MethodPtr method_ptr) {
  return {obj_ptr, method_ptr};
}

// Creates an action that invokes 'function_impl' with no argument.
template <typename FunctionImpl>
internal::InvokeWithoutArgsAction<typename std::decay<FunctionImpl>::type>
InvokeWithoutArgs(FunctionImpl function_impl) {
  return {std::move(function_impl)};
}

// Creates an action that invokes the given method on the given object
// with no argument.
template <class Class, typename MethodPtr>
internal::InvokeMethodWithoutArgsAction<Class, MethodPtr> InvokeWithoutArgs(
    Class* obj_ptr, MethodPtr method_ptr) {
  return {obj_ptr, method_ptr};
}

// Creates an action that performs an_action and throws away its
// result.  In other words, it changes the return type of an_action to
// void.  an_action MUST NOT return void, or the code won't compile.
template <typename A>
inline internal::IgnoreResultAction<A> IgnoreResult(const A& an_action) {
  return internal::IgnoreResultAction<A>(an_action);
}

// Creates a reference wrapper for the given L-value.  If necessary,
// you can explicitly specify the type of the reference.  For example,
// suppose 'derived' is an object of type Derived, ByRef(derived)
// would wrap a Derived&.  If you want to wrap a const Base& instead,
// where Base is a base class of Derived, just write:
//
//   ByRef<const Base>(derived)
//
// N.B. ByRef is redundant with std::ref, std::cref and std::reference_wrapper.
// However, it may still be used for consistency with ByMove().
template <typename T>
inline ::std::reference_wrapper<T> ByRef(T& l_value) {  // NOLINT
  return ::std::reference_wrapper<T>(l_value);
}

// The ReturnNew<T>(a1, a2, ..., a_k) action returns a pointer to a new
// instance of type T, constructed on the heap with constructor arguments
// a1, a2, ..., and a_k. The caller assumes ownership of the returned value.
template <typename T, typename... Params>
internal::ReturnNewAction<T, typename std::decay<Params>::type...> ReturnNew(
    Params&&... params) {
  return {std::forward_as_tuple(std::forward<Params>(params)...)};
}

// Action ReturnArg<k>() returns the k-th argument of the mock function.
template <size_t k>
internal::ReturnArgAction<k> ReturnArg() {
  return {};
}

// Action SaveArg<k>(pointer) saves the k-th (0-based) argument of the
// mock function to *pointer.
template <size_t k, typename Ptr>
internal::SaveArgAction<k, Ptr> SaveArg(Ptr pointer) {
  return {pointer};
}

// Action SaveArgPointee<k>(pointer) saves the value pointed to
// by the k-th (0-based) argument of the mock function to *pointer.
template <size_t k, typename Ptr>
internal::SaveArgPointeeAction<k, Ptr> SaveArgPointee(Ptr pointer) {
  return {pointer};
}

// Action SetArgReferee<k>(value) assigns 'value' to the variable
// referenced by the k-th (0-based) argument of the mock function.
template <size_t k, typename T>
internal::SetArgRefereeAction<k, typename std::decay<T>::type> SetArgReferee(
    T&& value) {
  return {std::forward<T>(value)};
}

// Action SetArrayArgument<k>(first, last) copies the elements in
// source range [first, last) to the array pointed to by the k-th
// (0-based) argument, which can be either a pointer or an
// iterator. The action does not take ownership of the elements in the
// source range.
template <size_t k, typename I1, typename I2>
internal::SetArrayArgumentAction<k, I1, I2> SetArrayArgument(I1 first,
                                                             I2 last) {
  return {first, last};
}

// Action DeleteArg<k>() deletes the k-th (0-based) argument of the mock
// function.
template <size_t k>
internal::DeleteArgAction<k> DeleteArg() {
  return {};
}

// This action returns the value pointed to by 'pointer'.
template <typename Ptr>
internal::ReturnPointeeAction<Ptr> ReturnPointee(Ptr pointer) {
  return {pointer};
}

// Action Throw(exception) can be used in a mock function of any type
// to throw the given exception.  Any copyable value can be thrown.
#if GTEST_HAS_EXCEPTIONS
template <typename T>
internal::ThrowAction<typename std::decay<T>::type> Throw(T&& exception) {
  return {std::forward<T>(exception)};
}
#endif  // GTEST_HAS_EXCEPTIONS

namespace internal {

// A macro from the ACTION* family (defined later in gmock-generated-actions.h)
// defines an action that can be used in a mock function.  Typically,
// these actions only care about a subset of the arguments of the mock
// function.  For example, if such an action only uses the second
// argument, it can be used in any mock function that takes >= 2
// arguments where the type of the second argument is compatible.
//
// Therefore, the action implementation must be prepared to take more
// arguments than it needs.  The ExcessiveArg type is used to
// represent those excessive arguments.  In order to keep the compiler
// error messages tractable, we define it in the testing namespace
// instead of testing::internal.  However, this is an INTERNAL TYPE
// and subject to change without notice, so a user MUST NOT USE THIS
// TYPE DIRECTLY.
struct ExcessiveArg {};

// Builds an implementation of an Action<> for some particular signature, using
// a class defined by an ACTION* macro.
template <typename F, typename Impl>
struct ActionImpl;

template <typename Impl>
struct ImplBase {
  struct Holder {
    // Allows each copy of the Action<> to get to the Impl.
    explicit operator const Impl&() const { return *ptr; }
    std::shared_ptr<Impl> ptr;
  };
  using type = typename std::conditional<std::is_constructible<Impl>::value,
                                         Impl, Holder>::type;
};

template <typename R, typename... Args, typename Impl>
struct ActionImpl<R(Args...), Impl> : ImplBase<Impl>::type {
  using Base = typename ImplBase<Impl>::type;
  using function_type = R(Args...);
  using args_type = std::tuple<Args...>;

  ActionImpl() = default;  // Only defined if appropriate for Base.
  explicit ActionImpl(std::shared_ptr<Impl> impl) : Base{std::move(impl)} {}

  R operator()(Args&&... arg) const {
    static constexpr size_t kMaxArgs =
        sizeof...(Args) <= 10 ? sizeof...(Args) : 10;
    return Apply(MakeIndexSequence<kMaxArgs>{},
                 MakeIndexSequence<10 - kMaxArgs>{},
                 args_type{std::forward<Args>(arg)...});
  }

  template <std::size_t... arg_id, std::size_t... excess_id>
  R Apply(IndexSequence<arg_id...>, IndexSequence<excess_id...>,
          const args_type& args) const {
    // Impl need not be specific to the signature of action being implemented;
    // only the implementing function body needs to have all of the specific
    // types instantiated.  Up to 10 of the args that are provided by the
    // args_type get passed, followed by a dummy of unspecified type for the
    // remainder up to 10 explicit args.
    static constexpr ExcessiveArg kExcessArg{};
    return static_cast<const Impl&>(*this)
        .template gmock_PerformImpl<
            /*function_type=*/function_type, /*return_type=*/R,
            /*args_type=*/args_type,
            /*argN_type=*/
            typename std::tuple_element<arg_id, args_type>::type...>(
            /*args=*/args, std::get<arg_id>(args)...,
            ((void)excess_id, kExcessArg)...);
  }
};

// Stores a default-constructed Impl as part of the Action<>'s
// std::function<>. The Impl should be trivial to copy.
template <typename F, typename Impl>
::testing::Action<F> MakeAction() {
  return ::testing::Action<F>(ActionImpl<F, Impl>());
}

// Stores just the one given instance of Impl.
template <typename F, typename Impl>
::testing::Action<F> MakeAction(std::shared_ptr<Impl> impl) {
  return ::testing::Action<F>(ActionImpl<F, Impl>(std::move(impl)));
}

#define GMOCK_INTERNAL_ARG_UNUSED(i, data, el) \
  , const arg##i##_type& arg##i GTEST_ATTRIBUTE_UNUSED_
#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_                 \
  const args_type& args GTEST_ATTRIBUTE_UNUSED_ GMOCK_PP_REPEAT( \
      GMOCK_INTERNAL_ARG_UNUSED, , 10)

#define GMOCK_INTERNAL_ARG(i, data, el) , const arg##i##_type& arg##i
#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_ \
  const args_type& args GMOCK_PP_REPEAT(GMOCK_INTERNAL_ARG, , 10)

#define GMOCK_INTERNAL_TEMPLATE_ARG(i, data, el) , typename arg##i##_type
#define GMOCK_ACTION_TEMPLATE_ARGS_NAMES_ \
  GMOCK_PP_TAIL(GMOCK_PP_REPEAT(GMOCK_INTERNAL_TEMPLATE_ARG, , 10))

#define GMOCK_INTERNAL_TYPENAME_PARAM(i, data, param) , typename param##_type
#define GMOCK_ACTION_TYPENAME_PARAMS_(params) \
  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPENAME_PARAM, , params))

#define GMOCK_INTERNAL_TYPE_PARAM(i, data, param) , param##_type
#define GMOCK_ACTION_TYPE_PARAMS_(params) \
  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_PARAM, , params))

#define GMOCK_INTERNAL_TYPE_GVALUE_PARAM(i, data, param) \
  , param##_type gmock_p##i
#define GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params) \
  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_GVALUE_PARAM, , params))

#define GMOCK_INTERNAL_GVALUE_PARAM(i, data, param) \
  , std::forward<param##_type>(gmock_p##i)
#define GMOCK_ACTION_GVALUE_PARAMS_(params) \
  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GVALUE_PARAM, , params))

#define GMOCK_INTERNAL_INIT_PARAM(i, data, param) \
  , param(::std::forward<param##_type>(gmock_p##i))
#define GMOCK_ACTION_INIT_PARAMS_(params) \
  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_INIT_PARAM, , params))

#define GMOCK_INTERNAL_FIELD_PARAM(i, data, param) param##_type param;
#define GMOCK_ACTION_FIELD_PARAMS_(params) \
  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_FIELD_PARAM, , params)

#define GMOCK_INTERNAL_ACTION(name, full_name, params)                         \
  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
  class full_name {                                                            \
   public:                                                                     \
    explicit full_name(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))               \
        : impl_(std::make_shared<gmock_Impl>(                                  \
              GMOCK_ACTION_GVALUE_PARAMS_(params))) {}                         \
    full_name(const full_name&) = default;                                     \
    full_name(full_name&&) noexcept = default;                                 \
    template <typename F>                                                      \
    operator ::testing::Action<F>() const {                                    \
      return ::testing::internal::MakeAction<F>(impl_);                        \
    }                                                                          \
                                                                               \
   private:                                                                    \
    class gmock_Impl {                                                         \
     public:                                                                   \
      explicit gmock_Impl(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))            \
          : GMOCK_ACTION_INIT_PARAMS_(params) {}                               \
      template <typename function_type, typename return_type,                  \
                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>         \
      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const;  \
      GMOCK_ACTION_FIELD_PARAMS_(params)                                       \
    };                                                                         \
    std::shared_ptr<const gmock_Impl> impl_;                                   \
  };                                                                           \
  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
  inline full_name<GMOCK_ACTION_TYPE_PARAMS_(params)> name(                    \
      GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params)) GTEST_MUST_USE_RESULT_;        \
  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
  inline full_name<GMOCK_ACTION_TYPE_PARAMS_(params)> name(                    \
      GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params)) {                              \
    return full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>(                       \
        GMOCK_ACTION_GVALUE_PARAMS_(params));                                  \
  }                                                                            \
  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
  template <typename function_type, typename return_type, typename args_type,  \
            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                 \
  return_type                                                                  \
  full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>::gmock_Impl::gmock_PerformImpl( \
      GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const

}  // namespace internal

// Similar to GMOCK_INTERNAL_ACTION, but no bound parameters are stored.
#define ACTION(name)                                                          \
  class name##Action {                                                        \
   public:                                                                    \
    explicit name##Action() noexcept {}                                       \
    name##Action(const name##Action&) noexcept {}                             \
    template <typename F>                                                     \
    operator ::testing::Action<F>() const {                                   \
      return ::testing::internal::MakeAction<F, gmock_Impl>();                \
    }                                                                         \
                                                                              \
   private:                                                                   \
    class gmock_Impl {                                                        \
     public:                                                                  \
      template <typename function_type, typename return_type,                 \
                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>        \
      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const; \
    };                                                                        \
  };                                                                          \
  inline name##Action name() GTEST_MUST_USE_RESULT_;                          \
  inline name##Action name() { return name##Action(); }                       \
  template <typename function_type, typename return_type, typename args_type, \
            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                \
  return_type name##Action::gmock_Impl::gmock_PerformImpl(                    \
      GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const

#define ACTION_P(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP, (__VA_ARGS__))

#define ACTION_P2(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP2, (__VA_ARGS__))

#define ACTION_P3(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP3, (__VA_ARGS__))

#define ACTION_P4(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP4, (__VA_ARGS__))

#define ACTION_P5(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP5, (__VA_ARGS__))

#define ACTION_P6(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP6, (__VA_ARGS__))

#define ACTION_P7(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP7, (__VA_ARGS__))

#define ACTION_P8(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP8, (__VA_ARGS__))

#define ACTION_P9(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP9, (__VA_ARGS__))

#define ACTION_P10(name, ...) \
  GMOCK_INTERNAL_ACTION(name, name##ActionP10, (__VA_ARGS__))

}  // namespace testing

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_