src/include/base/internal/cef_bind_internal.h

// Copyright (c) 2011 Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Do not include this header file directly. Use base/cef_bind.h instead.

#ifndef CEF_INCLUDE_BASE_INTERNAL_CEF_BIND_INTERNAL_H_
#define CEF_INCLUDE_BASE_INTERNAL_CEF_BIND_INTERNAL_H_

#include "include/base/cef_bind_helpers.h"
#include "include/base/cef_build.h"
#include "include/base/cef_template_util.h"
#include "include/base/cef_weak_ptr.h"
#include "include/base/internal/cef_callback_internal.h"
#include "include/base/internal/cef_raw_scoped_refptr_mismatch_checker.h"

#if defined(OS_WIN)
#include "include/base/internal/cef_bind_internal_win.h"
#endif

namespace base {
namespace cef_internal {

// See base/callback.h for user documentation.
//
//
// CONCEPTS:
//  Runnable -- A type (really a type class) that has a single Run() method
//              and a RunType typedef that corresponds to the type of Run().
//              A Runnable can declare that it should treated like a method
//              call by including a typedef named IsMethod.  The value of
//              this typedef is NOT inspected, only the existence.  When a
//              Runnable declares itself a method, Bind() will enforce special
//              refcounting + WeakPtr handling semantics for the first
//              parameter which is expected to be an object.
//  Functor -- A copyable type representing something that should be called.
//             All function pointers, Callback<>, and Runnables are functors
//             even if the invocation syntax differs.
//  RunType -- A function type (as opposed to function _pointer_ type) for
//             a Run() function.  Usually just a convenience typedef.
//  (Bound)ArgsType -- A function type that is being (ab)used to store the
//                     types of set of arguments.  The "return" type is always
//                     void here.  We use this hack so that we do not need
//                     a new type name for each arity of type. (eg.,
//                     BindState1, BindState2).  This makes forward
//                     declarations and friending much much easier.
//
// Types:
//  RunnableAdapter<> -- Wraps the various "function" pointer types into an
//                       object that adheres to the Runnable interface.
//                       There are |3*ARITY| RunnableAdapter types.
//  FunctionTraits<> -- Type traits that unwrap a function signature into a
//                      a set of easier to use typedefs.  Used mainly for
//                      compile time asserts.
//                      There are |ARITY| FunctionTraits types.
//  ForceVoidReturn<> -- Helper class for translating function signatures to
//                       equivalent forms with a "void" return type.
//                    There are |ARITY| ForceVoidReturn types.
//  FunctorTraits<> -- Type traits used determine the correct RunType and
//                     RunnableType for a Functor.  This is where function
//                     signature adapters are applied.
//                    There are |ARITY| ForceVoidReturn types.
//  MakeRunnable<> -- Takes a Functor and returns an object in the Runnable
//                    type class that represents the underlying Functor.
//                    There are |O(1)| MakeRunnable types.
//  InvokeHelper<> -- Take a Runnable + arguments and actully invokes it.
// Handle the differing syntaxes needed for WeakPtr<> support,
//                    and for ignoring return values.  This is separate from
//                    Invoker to avoid creating multiple version of Invoker<>
//                    which grows at O(n^2) with the arity.
//                    There are |k*ARITY| InvokeHelper types.
//  Invoker<> -- Unwraps the curried parameters and executes the Runnable.
//               There are |(ARITY^2 + ARITY)/2| Invoketypes.
//  BindState<> -- Stores the curried parameters, and is the main entry point
//                 into the Bind() system, doing most of the type resolution.
//                 There are ARITY BindState types.

// RunnableAdapter<>
//
// The RunnableAdapter<> templates provide a uniform interface for invoking
// a function pointer, method pointer, or const method pointer. The adapter
// exposes a Run() method with an appropriate signature. Using this wrapper
// allows for writing code that supports all three pointer types without
// undue repetition.  Without it, a lot of code would need to be repeated 3
// times.
//
// For method pointers and const method pointers the first argument to Run()
// is considered to be the received of the method.  This is similar to STL's
// mem_fun().
//
// This class also exposes a RunType typedef that is the function type of the
// Run() function.
//
// If and only if the wrapper contains a method or const method pointer, an
// IsMethod typedef is exposed.  The existence of this typedef (NOT the value)
// marks that the wrapper should be considered a method wrapper.

template <typename Functor>
class RunnableAdapter;

// Function: Arity 0.
template <typename R>
class RunnableAdapter<R (*)()> {
 public:
  typedef R(RunType)();

  explicit RunnableAdapter(R (*function)()) : function_(function) {}

  R Run() { return function_(); }

 private:
  R (*function_)();
};

// Method: Arity 0.
template <typename R, typename T>
class RunnableAdapter<R (T::*)()> {
 public:
  typedef R(RunType)(T*);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)()) : method_(method) {}

  R Run(T* object) { return (object->*method_)(); }

 private:
  R (T::*method_)();
};

// Const Method: Arity 0.
template <typename R, typename T>
class RunnableAdapter<R (T::*)() const> {
 public:
  typedef R(RunType)(const T*);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)() const) : method_(method) {}

  R Run(const T* object) { return (object->*method_)(); }

 private:
  R (T::*method_)() const;
};

// Function: Arity 1.
template <typename R, typename A1>
class RunnableAdapter<R (*)(A1)> {
 public:
  typedef R(RunType)(A1);

  explicit RunnableAdapter(R (*function)(A1)) : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1) {
    return function_(CallbackForward(a1));
  }

 private:
  R (*function_)(A1);
};

// Method: Arity 1.
template <typename R, typename T, typename A1>
class RunnableAdapter<R (T::*)(A1)> {
 public:
  typedef R(RunType)(T*, A1);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1)) : method_(method) {}

  R Run(T* object, typename CallbackParamTraits<A1>::ForwardType a1) {
    return (object->*method_)(CallbackForward(a1));
  }

 private:
  R (T::*method_)(A1);
};

// Const Method: Arity 1.
template <typename R, typename T, typename A1>
class RunnableAdapter<R (T::*)(A1) const> {
 public:
  typedef R(RunType)(const T*, A1);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1) const) : method_(method) {}

  R Run(const T* object, typename CallbackParamTraits<A1>::ForwardType a1) {
    return (object->*method_)(CallbackForward(a1));
  }

 private:
  R (T::*method_)(A1) const;
};

// Function: Arity 2.
template <typename R, typename A1, typename A2>
class RunnableAdapter<R (*)(A1, A2)> {
 public:
  typedef R(RunType)(A1, A2);

  explicit RunnableAdapter(R (*function)(A1, A2)) : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2) {
    return function_(CallbackForward(a1), CallbackForward(a2));
  }

 private:
  R (*function_)(A1, A2);
};

// Method: Arity 2.
template <typename R, typename T, typename A1, typename A2>
class RunnableAdapter<R (T::*)(A1, A2)> {
 public:
  typedef R(RunType)(T*, A1, A2);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2)) : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2));
  }

 private:
  R (T::*method_)(A1, A2);
};

// Const Method: Arity 2.
template <typename R, typename T, typename A1, typename A2>
class RunnableAdapter<R (T::*)(A1, A2) const> {
 public:
  typedef R(RunType)(const T*, A1, A2);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2) const) : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2));
  }

 private:
  R (T::*method_)(A1, A2) const;
};

// Function: Arity 3.
template <typename R, typename A1, typename A2, typename A3>
class RunnableAdapter<R (*)(A1, A2, A3)> {
 public:
  typedef R(RunType)(A1, A2, A3);

  explicit RunnableAdapter(R (*function)(A1, A2, A3)) : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3) {
    return function_(CallbackForward(a1), CallbackForward(a2),
                     CallbackForward(a3));
  }

 private:
  R (*function_)(A1, A2, A3);
};

// Method: Arity 3.
template <typename R, typename T, typename A1, typename A2, typename A3>
class RunnableAdapter<R (T::*)(A1, A2, A3)> {
 public:
  typedef R(RunType)(T*, A1, A2, A3);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3)) : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3));
  }

 private:
  R (T::*method_)(A1, A2, A3);
};

// Const Method: Arity 3.
template <typename R, typename T, typename A1, typename A2, typename A3>
class RunnableAdapter<R (T::*)(A1, A2, A3) const> {
 public:
  typedef R(RunType)(const T*, A1, A2, A3);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3) const)
      : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3));
  }

 private:
  R (T::*method_)(A1, A2, A3) const;
};

// Function: Arity 4.
template <typename R, typename A1, typename A2, typename A3, typename A4>
class RunnableAdapter<R (*)(A1, A2, A3, A4)> {
 public:
  typedef R(RunType)(A1, A2, A3, A4);

  explicit RunnableAdapter(R (*function)(A1, A2, A3, A4))
      : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4) {
    return function_(CallbackForward(a1), CallbackForward(a2),
                     CallbackForward(a3), CallbackForward(a4));
  }

 private:
  R (*function_)(A1, A2, A3, A4);
};

// Method: Arity 4.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4)> {
 public:
  typedef R(RunType)(T*, A1, A2, A3, A4);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4)) : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4);
};

// Const Method: Arity 4.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4) const> {
 public:
  typedef R(RunType)(const T*, A1, A2, A3, A4);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4) const)
      : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4) const;
};

// Function: Arity 5.
template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
class RunnableAdapter<R (*)(A1, A2, A3, A4, A5)> {
 public:
  typedef R(RunType)(A1, A2, A3, A4, A5);

  explicit RunnableAdapter(R (*function)(A1, A2, A3, A4, A5))
      : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5) {
    return function_(CallbackForward(a1), CallbackForward(a2),
                     CallbackForward(a3), CallbackForward(a4),
                     CallbackForward(a5));
  }

 private:
  R (*function_)(A1, A2, A3, A4, A5);
};

// Method: Arity 5.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5)> {
 public:
  typedef R(RunType)(T*, A1, A2, A3, A4, A5);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5))
      : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5);
};

// Const Method: Arity 5.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5) const> {
 public:
  typedef R(RunType)(const T*, A1, A2, A3, A4, A5);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5) const)
      : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5) const;
};

// Function: Arity 6.
template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
class RunnableAdapter<R (*)(A1, A2, A3, A4, A5, A6)> {
 public:
  typedef R(RunType)(A1, A2, A3, A4, A5, A6);

  explicit RunnableAdapter(R (*function)(A1, A2, A3, A4, A5, A6))
      : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6) {
    return function_(CallbackForward(a1), CallbackForward(a2),
                     CallbackForward(a3), CallbackForward(a4),
                     CallbackForward(a5), CallbackForward(a6));
  }

 private:
  R (*function_)(A1, A2, A3, A4, A5, A6);
};

// Method: Arity 6.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5, A6)> {
 public:
  typedef R(RunType)(T*, A1, A2, A3, A4, A5, A6);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5, A6))
      : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5), CallbackForward(a6));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5, A6);
};

// Const Method: Arity 6.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5, A6) const> {
 public:
  typedef R(RunType)(const T*, A1, A2, A3, A4, A5, A6);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5, A6) const)
      : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5), CallbackForward(a6));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5, A6) const;
};

// Function: Arity 7.
template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
class RunnableAdapter<R (*)(A1, A2, A3, A4, A5, A6, A7)> {
 public:
  typedef R(RunType)(A1, A2, A3, A4, A5, A6, A7);

  explicit RunnableAdapter(R (*function)(A1, A2, A3, A4, A5, A6, A7))
      : function_(function) {}

  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6,
        typename CallbackParamTraits<A7>::ForwardType a7) {
    return function_(CallbackForward(a1), CallbackForward(a2),
                     CallbackForward(a3), CallbackForward(a4),
                     CallbackForward(a5), CallbackForward(a6),
                     CallbackForward(a7));
  }

 private:
  R (*function_)(A1, A2, A3, A4, A5, A6, A7);
};

// Method: Arity 7.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5, A6, A7)> {
 public:
  typedef R(RunType)(T*, A1, A2, A3, A4, A5, A6, A7);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5, A6, A7))
      : method_(method) {}

  R Run(T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6,
        typename CallbackParamTraits<A7>::ForwardType a7) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5), CallbackForward(a6),
                              CallbackForward(a7));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5, A6, A7);
};

// Const Method: Arity 7.
template <typename R,
          typename T,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
class RunnableAdapter<R (T::*)(A1, A2, A3, A4, A5, A6, A7) const> {
 public:
  typedef R(RunType)(const T*, A1, A2, A3, A4, A5, A6, A7);
  typedef true_type IsMethod;

  explicit RunnableAdapter(R (T::*method)(A1, A2, A3, A4, A5, A6, A7) const)
      : method_(method) {}

  R Run(const T* object,
        typename CallbackParamTraits<A1>::ForwardType a1,
        typename CallbackParamTraits<A2>::ForwardType a2,
        typename CallbackParamTraits<A3>::ForwardType a3,
        typename CallbackParamTraits<A4>::ForwardType a4,
        typename CallbackParamTraits<A5>::ForwardType a5,
        typename CallbackParamTraits<A6>::ForwardType a6,
        typename CallbackParamTraits<A7>::ForwardType a7) {
    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
                              CallbackForward(a3), CallbackForward(a4),
                              CallbackForward(a5), CallbackForward(a6),
                              CallbackForward(a7));
  }

 private:
  R (T::*method_)(A1, A2, A3, A4, A5, A6, A7) const;
};

// FunctionTraits<>
//
// Breaks a function signature apart into typedefs for easier introspection.
template <typename Sig>
struct FunctionTraits;

template <typename R>
struct FunctionTraits<R()> {
  typedef R ReturnType;
};

template <typename R, typename A1>
struct FunctionTraits<R(A1)> {
  typedef R ReturnType;
  typedef A1 A1Type;
};

template <typename R, typename A1, typename A2>
struct FunctionTraits<R(A1, A2)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
};

template <typename R, typename A1, typename A2, typename A3>
struct FunctionTraits<R(A1, A2, A3)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
  typedef A3 A3Type;
};

template <typename R, typename A1, typename A2, typename A3, typename A4>
struct FunctionTraits<R(A1, A2, A3, A4)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
  typedef A3 A3Type;
  typedef A4 A4Type;
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
struct FunctionTraits<R(A1, A2, A3, A4, A5)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
  typedef A3 A3Type;
  typedef A4 A4Type;
  typedef A5 A5Type;
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
struct FunctionTraits<R(A1, A2, A3, A4, A5, A6)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
  typedef A3 A3Type;
  typedef A4 A4Type;
  typedef A5 A5Type;
  typedef A6 A6Type;
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
struct FunctionTraits<R(A1, A2, A3, A4, A5, A6, A7)> {
  typedef R ReturnType;
  typedef A1 A1Type;
  typedef A2 A2Type;
  typedef A3 A3Type;
  typedef A4 A4Type;
  typedef A5 A5Type;
  typedef A6 A6Type;
  typedef A7 A7Type;
};

// ForceVoidReturn<>
//
// Set of templates that support forcing the function return type to void.
template <typename Sig>
struct ForceVoidReturn;

template <typename R>
struct ForceVoidReturn<R()> {
  typedef void(RunType)();
};

template <typename R, typename A1>
struct ForceVoidReturn<R(A1)> {
  typedef void(RunType)(A1);
};

template <typename R, typename A1, typename A2>
struct ForceVoidReturn<R(A1, A2)> {
  typedef void(RunType)(A1, A2);
};

template <typename R, typename A1, typename A2, typename A3>
struct ForceVoidReturn<R(A1, A2, A3)> {
  typedef void(RunType)(A1, A2, A3);
};

template <typename R, typename A1, typename A2, typename A3, typename A4>
struct ForceVoidReturn<R(A1, A2, A3, A4)> {
  typedef void(RunType)(A1, A2, A3, A4);
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
struct ForceVoidReturn<R(A1, A2, A3, A4, A5)> {
  typedef void(RunType)(A1, A2, A3, A4, A5);
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
struct ForceVoidReturn<R(A1, A2, A3, A4, A5, A6)> {
  typedef void(RunType)(A1, A2, A3, A4, A5, A6);
};

template <typename R,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
struct ForceVoidReturn<R(A1, A2, A3, A4, A5, A6, A7)> {
  typedef void(RunType)(A1, A2, A3, A4, A5, A6, A7);
};

// FunctorTraits<>
//
// See description at top of file.
template <typename T>
struct FunctorTraits {
  typedef RunnableAdapter<T> RunnableType;
  typedef typename RunnableType::RunType RunType;
};

template <typename T>
struct FunctorTraits<IgnoreResultHelper<T>> {
  typedef typename FunctorTraits<T>::RunnableType RunnableType;
  typedef
      typename ForceVoidReturn<typename RunnableType::RunType>::RunType RunType;
};

template <typename T>
struct FunctorTraits<Callback<T>> {
  typedef Callback<T> RunnableType;
  typedef typename Callback<T>::RunType RunType;
};

// MakeRunnable<>
//
// Converts a passed in functor to a RunnableType using type inference.

template <typename T>
typename FunctorTraits<T>::RunnableType MakeRunnable(const T& t) {
  return RunnableAdapter<T>(t);
}

template <typename T>
typename FunctorTraits<T>::RunnableType MakeRunnable(
    const IgnoreResultHelper<T>& t) {
  return MakeRunnable(t.functor_);
}

template <typename T>
const typename FunctorTraits<Callback<T>>::RunnableType& MakeRunnable(
    const Callback<T>& t) {
  DCHECK(!t.is_null());
  return t;
}

// InvokeHelper<>
//
// There are 3 logical InvokeHelper<> specializations: normal, void-return,
// WeakCalls.
//
// The normal type just calls the underlying runnable.
//
// We need a InvokeHelper to handle void return types in order to support
// IgnoreResult().  Normally, if the Runnable's RunType had a void return,
// the template system would just accept "return functor.Run()" ignoring
// the fact that a void function is being used with return. This piece of
// sugar breaks though when the Runnable's RunType is not void.  Thus, we
// need a partial specialization to change the syntax to drop the "return"
// from the invocation call.
//
// WeakCalls similarly need special syntax that is applied to the first
// argument to check if they should no-op themselves.
template <bool IsWeakCall,
          typename ReturnType,
          typename Runnable,
          typename ArgsType>
struct InvokeHelper;

template <typename ReturnType, typename Runnable>
struct InvokeHelper<false, ReturnType, Runnable, void()> {
  static ReturnType MakeItSo(Runnable runnable) { return runnable.Run(); }
};

template <typename Runnable>
struct InvokeHelper<false, void, Runnable, void()> {
  static void MakeItSo(Runnable runnable) { runnable.Run(); }
};

template <typename ReturnType, typename Runnable, typename A1>
struct InvokeHelper<false, ReturnType, Runnable, void(A1)> {
  static ReturnType MakeItSo(Runnable runnable, A1 a1) {
    return runnable.Run(CallbackForward(a1));
  }
};

template <typename Runnable, typename A1>
struct InvokeHelper<false, void, Runnable, void(A1)> {
  static void MakeItSo(Runnable runnable, A1 a1) {
    runnable.Run(CallbackForward(a1));
  }
};

template <typename Runnable, typename BoundWeakPtr>
struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr)> {
  static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get());
  }
};

template <typename ReturnType, typename Runnable, typename A1, typename A2>
struct InvokeHelper<false, ReturnType, Runnable, void(A1, A2)> {
  static ReturnType MakeItSo(Runnable runnable, A1 a1, A2 a2) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2));
  }
};

template <typename Runnable, typename A1, typename A2>
struct InvokeHelper<false, void, Runnable, void(A1, A2)> {
  static void MakeItSo(Runnable runnable, A1 a1, A2 a2) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2));
  }
};

template <typename Runnable, typename BoundWeakPtr, typename A2>
struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, A2)> {
  static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr, A2 a2) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2));
  }
};

template <typename ReturnType,
          typename Runnable,
          typename A1,
          typename A2,
          typename A3>
struct InvokeHelper<false, ReturnType, Runnable, void(A1, A2, A3)> {
  static ReturnType MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
                        CallbackForward(a3));
  }
};

template <typename Runnable, typename A1, typename A2, typename A3>
struct InvokeHelper<false, void, Runnable, void(A1, A2, A3)> {
  static void MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3));
  }
};

template <typename Runnable, typename BoundWeakPtr, typename A2, typename A3>
struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, A2, A3)> {
  static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr, A2 a2, A3 a3) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2), CallbackForward(a3));
  }
};

template <typename ReturnType,
          typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4>
struct InvokeHelper<false, ReturnType, Runnable, void(A1, A2, A3, A4)> {
  static ReturnType MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
                        CallbackForward(a3), CallbackForward(a4));
  }
};

template <typename Runnable, typename A1, typename A2, typename A3, typename A4>
struct InvokeHelper<false, void, Runnable, void(A1, A2, A3, A4)> {
  static void MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4));
  }
};

template <typename Runnable,
          typename BoundWeakPtr,
          typename A2,
          typename A3,
          typename A4>
struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, A2, A3, A4)> {
  static void MakeItSo(Runnable runnable,
                       BoundWeakPtr weak_ptr,
                       A2 a2,
                       A3 a3,
                       A4 a4) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4));
  }
};

template <typename ReturnType,
          typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
struct InvokeHelper<false, ReturnType, Runnable, void(A1, A2, A3, A4, A5)> {
  static ReturnType MakeItSo(Runnable runnable,
                             A1 a1,
                             A2 a2,
                             A3 a3,
                             A4 a4,
                             A5 a5) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
                        CallbackForward(a3), CallbackForward(a4),
                        CallbackForward(a5));
  }
};

template <typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
struct InvokeHelper<false, void, Runnable, void(A1, A2, A3, A4, A5)> {
  static void MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5));
  }
};

template <typename Runnable,
          typename BoundWeakPtr,
          typename A2,
          typename A3,
          typename A4,
          typename A5>
struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, A2, A3, A4, A5)> {
  static void MakeItSo(Runnable runnable,
                       BoundWeakPtr weak_ptr,
                       A2 a2,
                       A3 a3,
                       A4 a4,
                       A5 a5) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5));
  }
};

template <typename ReturnType,
          typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
struct InvokeHelper<false, ReturnType, Runnable, void(A1, A2, A3, A4, A5, A6)> {
  static ReturnType
  MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5, A6 a6) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
                        CallbackForward(a3), CallbackForward(a4),
                        CallbackForward(a5), CallbackForward(a6));
  }
};

template <typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
struct InvokeHelper<false, void, Runnable, void(A1, A2, A3, A4, A5, A6)> {
  static void
  MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5, A6 a6) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5), CallbackForward(a6));
  }
};

template <typename Runnable,
          typename BoundWeakPtr,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6>
struct InvokeHelper<true,
                    void,
                    Runnable,
                    void(BoundWeakPtr, A2, A3, A4, A5, A6)> {
  static void MakeItSo(Runnable runnable,
                       BoundWeakPtr weak_ptr,
                       A2 a2,
                       A3 a3,
                       A4 a4,
                       A5 a5,
                       A6 a6) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5), CallbackForward(a6));
  }
};

template <typename ReturnType,
          typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
struct InvokeHelper<false,
                    ReturnType,
                    Runnable,
                    void(A1, A2, A3, A4, A5, A6, A7)> {
  static ReturnType
  MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5, A6 a6, A7 a7) {
    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
                        CallbackForward(a3), CallbackForward(a4),
                        CallbackForward(a5), CallbackForward(a6),
                        CallbackForward(a7));
  }
};

template <typename Runnable,
          typename A1,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
struct InvokeHelper<false, void, Runnable, void(A1, A2, A3, A4, A5, A6, A7)> {
  static void
  MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5, A6 a6, A7 a7) {
    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5), CallbackForward(a6),
                 CallbackForward(a7));
  }
};

template <typename Runnable,
          typename BoundWeakPtr,
          typename A2,
          typename A3,
          typename A4,
          typename A5,
          typename A6,
          typename A7>
struct InvokeHelper<true,
                    void,
                    Runnable,
                    void(BoundWeakPtr, A2, A3, A4, A5, A6, A7)> {
  static void MakeItSo(Runnable runnable,
                       BoundWeakPtr weak_ptr,
                       A2 a2,
                       A3 a3,
                       A4 a4,
                       A5 a5,
                       A6 a6,
                       A7 a7) {
    if (!weak_ptr.get()) {
      return;
    }
    runnable.Run(weak_ptr.get(), CallbackForward(a2), CallbackForward(a3),
                 CallbackForward(a4), CallbackForward(a5), CallbackForward(a6),
                 CallbackForward(a7));
  }
};

#if !defined(_MSC_VER)

template <typename ReturnType, typename Runnable, typename ArgsType>
struct InvokeHelper<true, ReturnType, Runnable, ArgsType> {
  // WeakCalls are only supported for functions with a void return type.
  // Otherwise, the function result would be undefined if the the WeakPtr<>
  // is invalidated.
  COMPILE_ASSERT(is_void<ReturnType>::value,
                 weak_ptrs_can_only_bind_to_methods_without_return_values);
};

#endif

// Invoker<>
//
// See description at the top of the file.
template <int NumBound, typename Storage, typename RunType>
struct Invoker;

// Arity 0 -> 0.
template <typename StorageType, typename R>
struct Invoker<0, StorageType, R()> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void()>::MakeItSo(storage->runnable_);
  }
};

// Arity 1 -> 1.
template <typename StorageType, typename R, typename X1>
struct Invoker<0, StorageType, R(X1)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType);

  typedef R(UnboundRunType)(X1);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename CallbackParamTraits<X1>::ForwardType
                                 x1)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1));
  }
};

// Arity 1 -> 0.
template <typename StorageType, typename R, typename X1>
struct Invoker<1, StorageType, R(X1)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1));
  }
};

// Arity 2 -> 2.
template <typename StorageType, typename R, typename X1, typename X2>
struct Invoker<0, StorageType, R(X1, X2)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType);

  typedef R(UnboundRunType)(X1, X2);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename CallbackParamTraits<X1>::ForwardType x1,
                             typename CallbackParamTraits<X2>::ForwardType
                                 x2)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2));
  }
};

// Arity 2 -> 1.
template <typename StorageType, typename R, typename X1, typename X2>
struct Invoker<1, StorageType, R(X1, X2)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType);

  typedef R(UnboundRunType)(X2);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X2>::ForwardType
                                 x2)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2));
  }
};

// Arity 2 -> 0.
template <typename StorageType, typename R, typename X1, typename X2>
struct Invoker<2, StorageType, R(X1, X2)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1), CallbackForward(x2));
  }
};

// Arity 3 -> 3.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3>
struct Invoker<0, StorageType, R(X1, X2, X3)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType);

  typedef R(UnboundRunType)(X1, X2, X3);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename CallbackParamTraits<X1>::ForwardType x1,
                             typename CallbackParamTraits<X2>::ForwardType x2,
                             typename CallbackParamTraits<X3>::ForwardType
                                 x3)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3));
  }
};

// Arity 3 -> 2.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3>
struct Invoker<1, StorageType, R(X1, X2, X3)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType);

  typedef R(UnboundRunType)(X2, X3);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X2>::ForwardType x2,
                             typename CallbackParamTraits<X3>::ForwardType
                                 x3)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3));
  }
};

// Arity 3 -> 1.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3>
struct Invoker<2, StorageType, R(X1, X2, X3)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X3>::ForwardType);

  typedef R(UnboundRunType)(X3);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X3>::ForwardType x3) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X3>::ForwardType
                                 x3)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3));
  }
};

// Arity 3 -> 0.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3>
struct Invoker<3, StorageType, R(X1, X2, X3)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename Bound3UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1), CallbackForward(x2),
                 CallbackForward(x3));
  }
};

// Arity 4 -> 4.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4>
struct Invoker<0, StorageType, R(X1, X2, X3, X4)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType);

  typedef R(UnboundRunType)(X1, X2, X3, X4);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename CallbackParamTraits<X1>::ForwardType x1,
                             typename CallbackParamTraits<X2>::ForwardType x2,
                             typename CallbackParamTraits<X3>::ForwardType x3,
                             typename CallbackParamTraits<X4>::ForwardType
                                 x4)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3),
                                                CallbackForward(x4));
  }
};

// Arity 4 -> 3.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4>
struct Invoker<1, StorageType, R(X1, X2, X3, X4)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType);

  typedef R(UnboundRunType)(X2, X3, X4);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X2>::ForwardType x2,
                             typename CallbackParamTraits<X3>::ForwardType x3,
                             typename CallbackParamTraits<X4>::ForwardType
                                 x4)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3),
                                                CallbackForward(x4));
  }
};

// Arity 4 -> 2.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4>
struct Invoker<2, StorageType, R(X1, X2, X3, X4)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType);

  typedef R(UnboundRunType)(X3, X4);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X3>::ForwardType x3,
                             typename CallbackParamTraits<X4>::ForwardType
                                 x4)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3),
                                                CallbackForward(x4));
  }
};

// Arity 4 -> 1.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4>
struct Invoker<3, StorageType, R(X1, X2, X3, X4)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X4>::ForwardType);

  typedef R(UnboundRunType)(X4);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X4>::ForwardType x4) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename Bound3UnwrapTraits::ForwardType,
                             typename CallbackParamTraits<X4>::ForwardType
                                 x4)>::MakeItSo(storage->runnable_,
                                                CallbackForward(x1),
                                                CallbackForward(x2),
                                                CallbackForward(x3),
                                                CallbackForward(x4));
  }
};

// Arity 4 -> 0.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4>
struct Invoker<4, StorageType, R(X1, X2, X3, X4)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename Bound3UnwrapTraits::ForwardType,
                             typename Bound4UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1), CallbackForward(x2),
                 CallbackForward(x3), CallbackForward(x4));
  }
};

// Arity 5 -> 5.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<0, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType);

  typedef R(UnboundRunType)(X1, X2, X3, X4, X5);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename CallbackParamTraits<X1>::ForwardType x1,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType
                 x5)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 5 -> 4.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<1, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType);

  typedef R(UnboundRunType)(X2, X3, X4, X5);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType
                 x5)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 5 -> 3.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<2, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType);

  typedef R(UnboundRunType)(X3, X4, X5);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType
                 x5)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 5 -> 2.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<3, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType);

  typedef R(UnboundRunType)(X4, X5);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType
                 x5)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 5 -> 1.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<4, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X5>::ForwardType);

  typedef R(UnboundRunType)(X5);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X5>::ForwardType x5) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename Bound4UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X5>::ForwardType
                 x5)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 5 -> 0.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5>
struct Invoker<5, StorageType, R(X1, X2, X3, X4, X5)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    typename Bound5UnwrapTraits::ForwardType x5 =
        Bound5UnwrapTraits::Unwrap(storage->p5_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename Bound3UnwrapTraits::ForwardType,
                             typename Bound4UnwrapTraits::ForwardType,
                             typename Bound5UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1), CallbackForward(x2),
                 CallbackForward(x3), CallbackForward(x4), CallbackForward(x5));
  }
};

// Arity 6 -> 6.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<0, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X1, X2, X3, X4, X5, X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename CallbackParamTraits<X1>::ForwardType x1,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 5.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<1, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X2, X3, X4, X5, X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 4.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<2, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X3, X4, X5, X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 3.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<3, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X4, X5, X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 2.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<4, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X5, X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename Bound4UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 1.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<5, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X6>::ForwardType);

  typedef R(UnboundRunType)(X6);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X6>::ForwardType x6) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    typename Bound5UnwrapTraits::ForwardType x5 =
        Bound5UnwrapTraits::Unwrap(storage->p5_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename Bound4UnwrapTraits::ForwardType,
             typename Bound5UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X6>::ForwardType
                 x6)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6));
  }
};

// Arity 6 -> 0.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6>
struct Invoker<6, StorageType, R(X1, X2, X3, X4, X5, X6)> {
  typedef R(RunType)(BindStateBase*);

  typedef R(UnboundRunType)();

  static R Run(BindStateBase* base) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;
    typedef typename StorageType::Bound6UnwrapTraits Bound6UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    typename Bound5UnwrapTraits::ForwardType x5 =
        Bound5UnwrapTraits::Unwrap(storage->p5_);
    typename Bound6UnwrapTraits::ForwardType x6 =
        Bound6UnwrapTraits::Unwrap(storage->p6_);
    return InvokeHelper<StorageType::IsWeakCall::value, R,
                        typename StorageType::RunnableType,
                        void(typename Bound1UnwrapTraits::ForwardType,
                             typename Bound2UnwrapTraits::ForwardType,
                             typename Bound3UnwrapTraits::ForwardType,
                             typename Bound4UnwrapTraits::ForwardType,
                             typename Bound5UnwrapTraits::ForwardType,
                             typename Bound6UnwrapTraits::ForwardType)>::
        MakeItSo(storage->runnable_, CallbackForward(x1), CallbackForward(x2),
                 CallbackForward(x3), CallbackForward(x4), CallbackForward(x5),
                 CallbackForward(x6));
  }
};

// Arity 7 -> 7.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6,
          typename X7>
struct Invoker<0, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X1>::ForwardType,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType,
                     typename CallbackParamTraits<X7>::ForwardType);

  typedef R(UnboundRunType)(X1, X2, X3, X4, X5, X6, X7);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X1>::ForwardType x1,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6,
               typename CallbackParamTraits<X7>::ForwardType x7) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.

    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename CallbackParamTraits<X1>::ForwardType x1,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType x6,
             typename CallbackParamTraits<X7>::ForwardType
                 x7)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6), CallbackForward(x7));
  }
};

// Arity 7 -> 6.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6,
          typename X7>
struct Invoker<1, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X2>::ForwardType,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType,
                     typename CallbackParamTraits<X7>::ForwardType);

  typedef R(UnboundRunType)(X2, X3, X4, X5, X6, X7);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X2>::ForwardType x2,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6,
               typename CallbackParamTraits<X7>::ForwardType x7) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X2>::ForwardType x2,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType x6,
             typename CallbackParamTraits<X7>::ForwardType
                 x7)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6), CallbackForward(x7));
  }
};

// Arity 7 -> 5.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6,
          typename X7>
struct Invoker<2, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X3>::ForwardType,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType,
                     typename CallbackParamTraits<X7>::ForwardType);

  typedef R(UnboundRunType)(X3, X4, X5, X6, X7);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X3>::ForwardType x3,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6,
               typename CallbackParamTraits<X7>::ForwardType x7) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X3>::ForwardType x3,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType x6,
             typename CallbackParamTraits<X7>::ForwardType
                 x7)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6), CallbackForward(x7));
  }
};

// Arity 7 -> 4.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6,
          typename X7>
struct Invoker<3, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X4>::ForwardType,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType,
                     typename CallbackParamTraits<X7>::ForwardType);

  typedef R(UnboundRunType)(X4, X5, X6, X7);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X4>::ForwardType x4,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6,
               typename CallbackParamTraits<X7>::ForwardType x7) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X4>::ForwardType x4,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType x6,
             typename CallbackParamTraits<X7>::ForwardType
                 x7)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6), CallbackForward(x7));
  }
};

// Arity 7 -> 3.
template <typename StorageType,
          typename R,
          typename X1,
          typename X2,
          typename X3,
          typename X4,
          typename X5,
          typename X6,
          typename X7>
struct Invoker<4, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
  typedef R(RunType)(BindStateBase*,
                     typename CallbackParamTraits<X5>::ForwardType,
                     typename CallbackParamTraits<X6>::ForwardType,
                     typename CallbackParamTraits<X7>::ForwardType);

  typedef R(UnboundRunType)(X5, X6, X7);

  static R Run(BindStateBase* base,
               typename CallbackParamTraits<X5>::ForwardType x5,
               typename CallbackParamTraits<X6>::ForwardType x6,
               typename CallbackParamTraits<X7>::ForwardType x7) {
    StorageType* storage = static_cast<StorageType*>(base);

    // Local references to make debugger stepping easier. If in a debugger,
    // you really want to warp ahead and step through the
    // InvokeHelper<>::MakeItSo() call below.
    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;

    typename Bound1UnwrapTraits::ForwardType x1 =
        Bound1UnwrapTraits::Unwrap(storage->p1_);
    typename Bound2UnwrapTraits::ForwardType x2 =
        Bound2UnwrapTraits::Unwrap(storage->p2_);
    typename Bound3UnwrapTraits::ForwardType x3 =
        Bound3UnwrapTraits::Unwrap(storage->p3_);
    typename Bound4UnwrapTraits::ForwardType x4 =
        Bound4UnwrapTraits::Unwrap(storage->p4_);
    return InvokeHelper<
        StorageType::IsWeakCall::value, R, typename StorageType::RunnableType,
        void(typename Bound1UnwrapTraits::ForwardType,
             typename Bound2UnwrapTraits::ForwardType,
             typename Bound3UnwrapTraits::ForwardType,
             typename Bound4UnwrapTraits::ForwardType,
             typename CallbackParamTraits<X5>::ForwardType x5,
             typename CallbackParamTraits<X6>::ForwardType x6,
             typename CallbackParamTraits<X7>::ForwardType
                 x7)>::MakeItSo(storage->runnable_, CallbackForward(x1),
                                CallbackForward(x2), CallbackForward(x3),
                                CallbackForward(x4), CallbackForward(x5),
                                CallbackForward(x6), CallbackForward(x7));
  }
};

// Arity 7 -> 2.
template <typename StorageType,
          typename R,