include/gmock/gmock-actions.h

// Copyright 2007, Google Inc.
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// modification, are permitted provided that the following conditions are
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//
//     * Redistributions of source code must retain the above copyright
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// Author: wan@google.com (Zhanyong Wan)

// Google Mock - a framework for writing C++ mock classes.
//
// This file implements some commonly used actions.

#ifndef GMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
#define GMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_

#include <algorithm>
#include <string>
#include <errno.h>
#include <gmock/internal/gmock-internal-utils.h>
#include <gmock/internal/gmock-port.h>

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 {

template <typename F>
class MonomorphicDoDefaultActionImpl;

template <typename F1, typename F2>
class ActionAdaptor;

// BuiltInDefaultValue<T>::Get() returns the "built-in" default
// value for type T, which is NULL when T is a pointer type, 0 when T
// is a numeric type, false when T is bool, or "" when T is string or
// std::string.  For any other type T, this value is undefined and the
// function will abort the process.
template <typename T>
class BuiltInDefaultValue {
 public:
  // This function returns true iff type T has a built-in default value.
  static bool Exists() { return 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.
  }
};

// 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 NULL; }
};

// 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
#if GTEST_HAS_GLOBAL_STRING
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE(::string, "");
#endif  // GTEST_HAS_GLOBAL_STRING
#if GTEST_HAS_STD_STRING
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE(::std::string, "");
#endif  // GTEST_HAS_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');

// signed wchar_t and unsigned wchar_t are NOT in the C++ standard.
// Using them is a bad practice and not portable.  So don't use them.
//
// Still, Google Mock is designed to work even if the user uses signed
// wchar_t or unsigned wchar_t (obviously, assuming the compiler
// supports them).
//
// To gcc,
//
//   wchar_t == signed wchar_t != unsigned wchar_t == unsigned int
//
// MSVC does not recognize signed wchar_t or unsigned wchar_t.  It
// treats wchar_t as a native type usually, but treats it as the same
// as unsigned short when the compiler option /Zc:wchar_t- is
// specified.
//
// Therefore we provide a default action for wchar_t when compiled
// with gcc or _NATIVE_WCHAR_T_DEFINED is defined.
//
// 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 defined(__GNUC__) || defined(_NATIVE_WCHAR_T_DEFINED)
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(UInt64, 0);
GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE(Int64, 0);
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

}  // 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 value_;
    value_ = new T(x);
  }

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

  // Returns true iff the user has set the default value for type T.
  static bool IsSet() { return value_ != NULL; }

  // 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 value_ == NULL ?
        internal::BuiltInDefaultValue<T>::Get() : *value_;
  }
 private:
  static const T* value_;
};

// 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_ = NULL;
  }

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

  // 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_ == NULL ?
        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>
const T* DefaultValue<T>::value_ = NULL;

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

// 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() : is_do_default_(false) {}

  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;

  // Returns true iff this is the DoDefault() action.
  bool IsDoDefault() const { return is_do_default_; }
 private:
  template <typename Function>
  friend class internal::MonomorphicDoDefaultActionImpl;

  // This private constructor is reserved for implementing
  // DoDefault(), the default action for a given mock function.
  explicit ActionInterface(bool is_do_default)
      : is_do_default_(is_do_default) {}

  // True iff this action is DoDefault().
  const bool is_do_default_;
};

// 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
// linked_ptr to const ActionInterface<T>, so copying is fairly cheap.
// 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 {
 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() : impl_(NULL) {}

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

  // Copy constructor.
  Action(const Action& action) : impl_(action.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 cann be implicitly converted to
  // F's.
  template <typename Func>
  explicit Action(const Action<Func>& action);

  // Returns true iff this is the DoDefault() action.
  bool IsDoDefault() const { return impl_->IsDoDefault(); }

  // 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(const ArgumentTuple& args) const {
    return impl_->Perform(args);
  }
 private:
  template <typename F1, typename F2>
  friend class internal::ActionAdaptor;

  internal::linked_ptr<ActionInterface<F> > impl_;
};

// 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
//       // tr1::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) {}

    virtual Result Perform(const ArgumentTuple& args) {
      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 {

// Allows an Action<F2> object to pose as an Action<F1>, as long as F2
// and F1 are compatible.
template <typename F1, typename F2>
class ActionAdaptor : public ActionInterface<F1> {
 public:
  typedef typename internal::Function<F1>::Result Result;
  typedef typename internal::Function<F1>::ArgumentTuple ArgumentTuple;

  explicit ActionAdaptor(const Action<F2>& from) : impl_(from.impl_) {}

  virtual Result Perform(const ArgumentTuple& args) {
    return impl_->Perform(args);
  }
 private:
  const internal::linked_ptr<ActionInterface<F2> > impl_;
};

// Implements the polymorphic Return(x) action, which can be used in
// any function that returns the type of x, regardless of the argument
// types.
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_(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 {
    // 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;
    GMOCK_COMPILE_ASSERT(!internal::is_reference<Result>::value,
                         use_ReturnRef_instead_of_Return_to_return_a_reference);
    return Action<F>(new Impl<F>(value_));
  }
 private:
  // Implements the Return(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(R value) : value_(value) {}

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

   private:
    R value_;
  };

  R value_;
};

// Implements the ReturnNull() action.
class ReturnNullAction {
 public:
  // Allows ReturnNull() to be used in any pointer-returning function.
  template <typename Result, typename ArgumentTuple>
  static Result Perform(const ArgumentTuple&) {
    GMOCK_COMPILE_ASSERT(internal::is_pointer<Result>::value,
                   ReturnNull_can_be_used_to_return_a_pointer_only);
    return NULL;
  }
};

// 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&) {
    CompileAssertTypesEqual<void, Result>();
  }
};

// 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.
    GMOCK_COMPILE_ASSERT(internal::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

    virtual Result Perform(const ArgumentTuple&) {
      return ref_;
    }
   private:
    T& ref_;
  };

  T& ref_;
};

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

  MonomorphicDoDefaultActionImpl() : ActionInterface<F>(true) {}

  // For technical reasons, DoDefault() cannot be used inside a
  // composite action (e.g. DoAll(...)).  It can only be used at the
  // top level in an EXPECT_CALL().  If this function is called, the
  // user must be using DoDefault() inside a composite action, and we
  // have to generate a run-time error.
  virtual Result Perform(const ArgumentTuple&) {
    Assert(false, __FILE__, __LINE__,
           "You are using DoDefault() inside a composite action like "
           "DoAll() or WithArgs().  This is not supported for technical "
           "reasons.  Please instead spell out the default action, or "
           "assign the default action to an Action variable and use "
           "the variable in various places.");
    return internal::Invalid<Result>();
    // The above statement will never be reached, but is required in
    // order for this function to compile.
  }
};

// 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>(new MonomorphicDoDefaultActionImpl<F>);
  }
};

// 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_;
};

// 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_;
};

// Implements the SetArgumentPointee<N>(x) action for any function
// whose N-th argument (0-based) is a pointer to x's type.  The
// template parameter kIsProto is true iff type A is ProtocolMessage,
// proto2::Message, or a sub-class of those.
template <size_t N, typename A, bool kIsProto>
class SetArgumentPointeeAction {
 public:
  // Constructs an action that sets the variable pointed to by the
  // N-th function argument to 'value'.
  explicit SetArgumentPointeeAction(const A& value) : value_(value) {}

  template <typename Result, typename ArgumentTuple>
  void Perform(const ArgumentTuple& args) const {
    CompileAssertTypesEqual<void, Result>();
    *::std::tr1::get<N>(args) = value_;
  }

 private:
  const A value_;
};

template <size_t N, typename Proto>
class SetArgumentPointeeAction<N, Proto, true> {
 public:
  // Constructs an action that sets the variable pointed to by the
  // N-th function argument to 'proto'.  Both ProtocolMessage and
  // proto2::Message have the CopyFrom() method, so the same
  // implementation works for both.
  explicit SetArgumentPointeeAction(const Proto& proto) : proto_(new Proto) {
    proto_->CopyFrom(proto);
  }

  template <typename Result, typename ArgumentTuple>
  void Perform(const ArgumentTuple& args) const {
    CompileAssertTypesEqual<void, Result>();
    ::std::tr1::get<N>(args)->CopyFrom(*proto_);
  }
 private:
  const internal::linked_ptr<Proto> proto_;
};

// Implements the SetArrayArgument<N>(first, last) action for any function
// whose N-th argument (0-based) is a pointer or iterator to a type that can be
// implicitly converted from *first.
template <size_t N, typename InputIterator>
class SetArrayArgumentAction {
 public:
  // Constructs an action that sets the variable pointed to by the
  // N-th function argument to 'value'.
  explicit SetArrayArgumentAction(InputIterator first, InputIterator last)
      : first_(first), last_(last) {
  }

  template <typename Result, typename ArgumentTuple>
  void Perform(const ArgumentTuple& args) const {
    CompileAssertTypesEqual<void, Result>();

    // Microsoft compiler deprecates ::std::copy, so we want to suppress warning
    // 4996 (Function call with parameters that may be unsafe) there.
#ifdef GTEST_OS_WINDOWS
#pragma warning(push)          // Saves the current warning state.
#pragma warning(disable:4996)  // Temporarily disables warning 4996.
#endif  // GTEST_OS_WINDOWS
    ::std::copy(first_, last_, ::std::tr1::get<N>(args));
#ifdef GTEST_OS_WINDOWS
#pragma warning(pop)           // Restores the warning state.
#endif  // GTEST_OS_WINDOWS
  }

 private:
  const InputIterator first_;
  const InputIterator last_;
};

// 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 (i.e. f can be
// assigned to a tr1::function<F>).
template <typename FunctionImpl>
class InvokeWithoutArgsAction {
 public:
  // The c'tor makes a copy of function_impl (either a function
  // pointer or a functor).
  explicit InvokeWithoutArgsAction(FunctionImpl function_impl)
      : function_impl_(function_impl) {}

  // Allows InvokeWithoutArgs(f) to be used as any action whose type is
  // compatible with f.
  template <typename Result, typename ArgumentTuple>
  Result Perform(const ArgumentTuple&) { return function_impl_(); }
 private:
  FunctionImpl function_impl_;
};

// Implements the InvokeWithoutArgs(object_ptr, &Class::Method) action.
template <class Class, typename MethodPtr>
class InvokeMethodWithoutArgsAction {
 public:
  InvokeMethodWithoutArgsAction(Class* obj_ptr, MethodPtr method_ptr)
      : obj_ptr_(obj_ptr), method_ptr_(method_ptr) {}

  template <typename Result, typename ArgumentTuple>
  Result Perform(const ArgumentTuple&) const {
    return (obj_ptr_->*method_ptr_)();
  }
 private:
  Class* const obj_ptr_;
  const MethodPtr 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.
    CompileAssertTypesEqual<void, Result>();

    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) {}

    virtual void Perform(const ArgumentTuple& args) {
      // 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_;
};

}  // 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);
//   }
//   ...
//   EXEPCT_CALL(mock, Foo("abc", _, _))
//       .WillOnce(Invoke(DistanceToOriginWithLabel));
//   EXEPCT_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);
//   }
//   ...
//   EXEPCT_CALL(mock, Foo("abc", _, _)).WillOnce(Invoke(DistanceToOrigin));
//   EXEPCT_CALL(mock, Bar(5, _, _)).WillOnce(Invoke(DistanceToOrigin));
typedef internal::IgnoredValue Unused;

// This constructor allows us to turn an Action<From> object into an
// Action<To>, as long as To's arguments can be implicitly converted
// to From's and From's return type cann be implicitly converted to
// To's.
template <typename To>
template <typename From>
Action<To>::Action(const Action<From>& from)
    : impl_(new internal::ActionAdaptor<To, From>(from)) {}

// 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>(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);
}

// 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>
PolymorphicAction<
  internal::SetArgumentPointeeAction<
    N, T, internal::IsAProtocolMessage<T>::value> >
SetArgumentPointee(const T& x) {
  return MakePolymorphicAction(internal::SetArgumentPointeeAction<
      N, T, internal::IsAProtocolMessage<T>::value>(x));
}

// Creates an action that sets the elements of the array pointed to by the N-th
// (0-based) function argument, which can be either a pointer or an iterator,
// to the values of the elements in the source range [first, last).
template <size_t N, typename InputIterator>
PolymorphicAction<internal::SetArrayArgumentAction<N, InputIterator> >
SetArrayArgument(InputIterator first, InputIterator last) {
  return MakePolymorphicAction(internal::SetArrayArgumentAction<
      N, InputIterator>(first, last));
}

// 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));
}

// 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));
}

// Various overloads for InvokeWithoutArgs().

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

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

}  // namespace testing

#endif  // GMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_