Bind: Use Variadic Templates in bind_internal.h

* Introduce TypeList as helpers.
* Drop bind_internal.h.pump and replace generated codes with Variadic Templates version.

BUG=433164

Review URL: https://codereview.chromium.org/743853002

Cr-Commit-Position: refs/heads/master@{#314847}

5 files changed, 178 insertions, 2315 deletions

diff --git a/base/bind.h b/base/bind.h
index 7874656..51be10d 100644
--- a/base/bind.h
+++ b/base/bind.h
@@ -52,13 +52,14 @@ base::Callback<
     typename internal::BindState<
         typename internal::FunctorTraits<Functor>::RunnableType,
         typename internal::FunctorTraits<Functor>::RunType,
-        void()>::UnboundRunType>
+        internal::TypeList<>>::UnboundRunType>
 Bind(Functor functor) {
   // Typedefs for how to store and run the functor.
   typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType;
   typedef typename internal::FunctorTraits<Functor>::RunType RunType;
 
-  typedef internal::BindState<RunnableType, RunType, void()> BindState;
+  typedef internal::BindState<RunnableType, RunType,
+                              internal::TypeList<>> BindState;
 
   return Callback<typename BindState::UnboundRunType>(
       new BindState(internal::MakeRunnable(functor)));
@@ -69,7 +70,8 @@ base::Callback<
     typename internal::BindState<
         typename internal::FunctorTraits<Functor>::RunnableType,
         typename internal::FunctorTraits<Functor>::RunType,
-        void(typename internal::CallbackParamTraits<Args>::StorageType...)>
+        internal::TypeList<
+            typename internal::CallbackParamTraits<Args>::StorageType...>>
             ::UnboundRunType>
 Bind(Functor functor, const Args&... args) {
   // Typedefs for how to store and run the functor.
@@ -101,8 +103,10 @@ Bind(Functor functor, const Args&... args) {
       !internal::HasRefCountedParamAsRawPtr<is_method, Args...>::value,
       "a_parameter_is_refcounted_type_and_needs_scoped_refptr");
 
-  typedef internal::BindState<RunnableType, RunType,
-      void(typename internal::CallbackParamTraits<Args>::StorageType...)>
+  typedef internal::BindState<
+      RunnableType, RunType,
+      internal::TypeList<
+          typename internal::CallbackParamTraits<Args>::StorageType...>>
       BindState;
 
   return Callback<typename BindState::UnboundRunType>(
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index f3efc31..f8e89bd 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -435,45 +435,46 @@ struct UnwrapTraits<PassedWrapper<T> > {
 
 // Utility for handling different refcounting semantics in the Bind()
 // function.
-template <bool is_method, typename T>
-struct MaybeRefcount;
+template <bool is_method, typename... T>
+struct MaybeScopedRefPtr;
 
-template <typename T>
-struct MaybeRefcount<false, T> {
-  static void AddRef(const T&) {}
-  static void Release(const T&) {}
+template <bool is_method>
+struct MaybeScopedRefPtr<is_method> {
+  MaybeScopedRefPtr() {}
 };
 
-template <typename T, size_t n>
-struct MaybeRefcount<false, T[n]> {
-  static void AddRef(const T*) {}
-  static void Release(const T*) {}
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<false, T, Rest...> {
+  MaybeScopedRefPtr(const T&, const Rest&...) {}
 };
 
-template <typename T>
-struct MaybeRefcount<true, T> {
-  static void AddRef(const T&) {}
-  static void Release(const T&) {}
+template <typename T, size_t n, typename... Rest>
+struct MaybeScopedRefPtr<false, T[n], Rest...> {
+  MaybeScopedRefPtr(const T*, const Rest&...) {}
 };
 
-template <typename T>
-struct MaybeRefcount<true, T*> {
-  static void AddRef(T* o) { o->AddRef(); }
-  static void Release(T* o) { o->Release(); }
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, T, Rest...> {
+  MaybeScopedRefPtr(const T& o, const Rest&...) {}
+};
+
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, T*, Rest...> {
+  MaybeScopedRefPtr(T* o, const Rest&...) : ref_(o) {}
+  scoped_refptr<T> ref_;
 };
 
 // No need to additionally AddRef() and Release() since we are storing a
 // scoped_refptr<> inside the storage object already.
-template <typename T>
-struct MaybeRefcount<true, scoped_refptr<T> > {
-  static void AddRef(const scoped_refptr<T>& o) {}
-  static void Release(const scoped_refptr<T>& o) {}
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, scoped_refptr<T>, Rest...> {
+  MaybeScopedRefPtr(const scoped_refptr<T>&, const Rest&...) {}
 };
 
-template <typename T>
-struct MaybeRefcount<true, const T*> {
-  static void AddRef(const T* o) { o->AddRef(); }
-  static void Release(const T* o) { o->Release(); }
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, const T*, Rest...> {
+  MaybeScopedRefPtr(const T* o, const Rest&...) : ref_(o) {}
+  scoped_refptr<const T> ref_;
 };
 
 // IsWeakMethod is a helper that determine if we are binding a WeakPtr<> to a
@@ -481,15 +482,89 @@ struct MaybeRefcount<true, const T*> {
 // InvokeHelper that will no-op itself in the event the WeakPtr<> for
 // the target object is invalidated.
 //
-// P1 should be the type of the object that will be received of the method.
-template <bool IsMethod, typename P1>
+// The first argument should be the type of the object that will be received by
+// the method.
+template <bool IsMethod, typename... Args>
 struct IsWeakMethod : public false_type {};
 
-template <typename T>
-struct IsWeakMethod<true, WeakPtr<T> > : public true_type {};
+template <typename T, typename... Args>
+struct IsWeakMethod<true, WeakPtr<T>, Args...> : public true_type {};
 
-template <typename T>
-struct IsWeakMethod<true, ConstRefWrapper<WeakPtr<T> > > : public true_type {};
+template <typename T, typename... Args>
+struct IsWeakMethod<true, ConstRefWrapper<WeakPtr<T>>, Args...>
+    : public true_type {};
+
+
+// Packs a list of types to hold them in a single type.
+template <typename... Types>
+struct TypeList {};
+
+// Used for DropTypeListItem implementation.
+template <size_t n, typename List>
+struct DropTypeListItemImpl;
+
+// Do not use enable_if and SFINAE here to avoid MSVC2013 compile failure.
+template <size_t n, typename T, typename... List>
+struct DropTypeListItemImpl<n, TypeList<T, List...>>
+    : DropTypeListItemImpl<n - 1, TypeList<List...>> {};
+
+template <typename T, typename... List>
+struct DropTypeListItemImpl<0, TypeList<T, List...>> {
+  typedef TypeList<T, List...> Type;
+};
+
+template <>
+struct DropTypeListItemImpl<0, TypeList<>> {
+  typedef TypeList<> Type;
+};
+
+// A type-level function that drops |n| list item from given TypeList.
+template <size_t n, typename List>
+using DropTypeListItem = typename DropTypeListItemImpl<n, List>::Type;
+
+// Used for ConcatTypeLists implementation.
+template <typename List1, typename List2>
+struct ConcatTypeListsImpl;
+
+template <typename... Types1, typename... Types2>
+struct ConcatTypeListsImpl<TypeList<Types1...>, TypeList<Types2...>> {
+  typedef TypeList<Types1..., Types2...> Type;
+};
+
+// A type-level function that concats two TypeLists.
+template <typename List1, typename List2>
+using ConcatTypeLists = typename ConcatTypeListsImpl<List1, List2>::Type;
+
+template <size_t n, typename List>
+struct NthTypeImpl;
+
+template <size_t n, typename T, typename... Types>
+struct NthTypeImpl<n, TypeList<T, Types...>>
+    : NthTypeImpl<n - 1, TypeList<Types...>> {
+};
+
+template <typename T, typename... Types>
+struct NthTypeImpl<0, TypeList<T, Types...>> {
+  typedef T Type;
+};
+
+// A type-level function that extracts |n|th type from a TypeList.
+template <size_t n, typename List>
+using NthType = typename NthTypeImpl<n, List>::Type;
+
+// Used for MakeFunctionType implementation.
+template <typename R, typename ArgList>
+struct MakeFunctionTypeImpl;
+
+template <typename R, typename... Args>
+struct MakeFunctionTypeImpl<R, TypeList<Args...>> {
+  typedef R(Type)(Args...);
+};
+
+// A type-level function that constructs a function type that has |R| as its
+// return type and has TypeLists items as its arguments.
+template <typename R, typename ArgList>
+using MakeFunctionType = typename MakeFunctionTypeImpl<R, ArgList>::Type;
 
 }  // namespace internal
 
diff --git a/base/bind_internal.h b/base/bind_internal.h
index b568c16..5fc1459 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -1,8 +1,3 @@
-// This file was GENERATED by command:
-//     pump.py bind_internal.h.pump
-// DO NOT EDIT BY HAND!!!
-
-
 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
@@ -15,6 +10,7 @@
 #include "base/memory/raw_scoped_refptr_mismatch_checker.h"
 #include "base/memory/weak_ptr.h"
 #include "base/template_util.h"
+#include "base/tuple.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
@@ -51,10 +47,6 @@ namespace internal {
 // Types:
 //  RunnableAdapter<> -- Wraps the various "function" pointer types into an
 //                       object that adheres to the Runnable interface.
-//  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.
 //  FunctorTraits<> -- Type traits used determine the correct RunType and
@@ -64,12 +56,11 @@ namespace internal {
 //                    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.
+//                    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<>.
 //  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.
@@ -209,84 +200,6 @@ class RunnableAdapter<R(T::*)(Args...) const> {
   R (T::*method_)(Args...) const;
 };
 
-// TODO(tzik): Remove FunctionTraits after we finish removing bind.pump.
-// 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<>
 //
@@ -310,14 +223,14 @@ struct FunctorTraits {
 };
 
 template <typename T>
-struct FunctorTraits<IgnoreResultHelper<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> > {
+struct FunctorTraits<Callback<T>> {
   typedef Callback<T> RunnableType;
   typedef typename Callback<T>::RunType RunType;
 };
@@ -339,7 +252,7 @@ MakeRunnable(const IgnoreResultHelper<T>& t) {
 }
 
 template <typename T>
-const typename FunctorTraits<Callback<T> >::RunnableType&
+const typename FunctorTraits<Callback<T>>::RunnableType&
 MakeRunnable(const Callback<T>& t) {
   DCHECK(!t.is_null());
   return t;
@@ -368,22 +281,21 @@ template <bool IsWeakCall, typename ReturnType, typename Runnable,
 struct InvokeHelper;
 
 template <typename ReturnType, typename Runnable, typename... Args>
-struct InvokeHelper<false, ReturnType, Runnable,
-    void(Args...)>  {
+struct InvokeHelper<false, ReturnType, Runnable, TypeList<Args...>> {
   static ReturnType MakeItSo(Runnable runnable, Args... args) {
     return runnable.Run(CallbackForward(args)...);
   }
 };
 
 template <typename Runnable, typename... Args>
-struct InvokeHelper<false, void, Runnable, void(Args...)>  {
+struct InvokeHelper<false, void, Runnable, TypeList<Args...>> {
   static void MakeItSo(Runnable runnable, Args... args) {
     runnable.Run(CallbackForward(args)...);
   }
 };
 
 template <typename Runnable, typename BoundWeakPtr, typename... Args>
-struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, Args...)>  {
+struct InvokeHelper<true, void, Runnable, TypeList<BoundWeakPtr, Args...>> {
   static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr, Args... args) {
     if (!weak_ptr.get()) {
       return;
@@ -408,1419 +320,30 @@ struct InvokeHelper<true, ReturnType, Runnable, ArgsType> {
 // Invoker<>
 //
 // See description at the top of the file.
-template <int NumBound, typename Storage, typename RunType>
+template <typename BoundIndices,
+          typename StorageType, typename Unwrappers,
+          typename InvokeHelperType, typename UnboundForwardRunType>
 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);
-
+template <size_t... bound_indices,
+          typename StorageType,
+          typename... Unwrappers,
+          typename InvokeHelperType,
+          typename R,
+          typename... UnboundForwardArgs>
+struct Invoker<IndexSequence<bound_indices...>,
+               StorageType, TypeList<Unwrappers...>,
+               InvokeHelperType, R(UnboundForwardArgs...)> {
   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) {
+               UnboundForwardArgs... unbound_args) {
     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,typename X1, typename X2,
-    typename X3, typename X4, typename X5, typename X6, typename X7>
-struct Invoker<5, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
-  typedef R(RunType)(BindStateBase*,
-      typename CallbackParamTraits<X6>::ForwardType,
-      typename CallbackParamTraits<X7>::ForwardType);
-
-  typedef R(UnboundRunType)(X6, X7);
-
-  static R Run(BindStateBase* base,
-      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;
-    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,
-               typename CallbackParamTraits<X7>::ForwardType x7)>
-               ::MakeItSo(storage->runnable_, CallbackForward(x1),
-                   CallbackForward(x2), CallbackForward(x3),
-                   CallbackForward(x4), CallbackForward(x5),
-                   CallbackForward(x6), CallbackForward(x7));
-  }
-};
-
-// Arity 7 -> 1.
-template <typename StorageType, typename R,typename X1, typename X2,
-    typename X3, typename X4, typename X5, typename X6, typename X7>
-struct Invoker<6, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
-  typedef R(RunType)(BindStateBase*,
-      typename CallbackParamTraits<X7>::ForwardType);
-
-  typedef R(UnboundRunType)(X7);
-
-  static R Run(BindStateBase* base,
-      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;
-    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,
-               typename CallbackParamTraits<X7>::ForwardType x7)>
-               ::MakeItSo(storage->runnable_, CallbackForward(x1),
-                   CallbackForward(x2), CallbackForward(x3),
-                   CallbackForward(x4), CallbackForward(x5),
-                   CallbackForward(x6), CallbackForward(x7));
-  }
-};
-
-// Arity 7 -> 0.
-template <typename StorageType, typename R,typename X1, typename X2,
-    typename X3, typename X4, typename X5, typename X6, typename X7>
-struct Invoker<7, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
-  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;
-    typedef typename StorageType::Bound7UnwrapTraits Bound7UnwrapTraits;
-
-    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_);
-    typename Bound7UnwrapTraits::ForwardType x7 =
-        Bound7UnwrapTraits::Unwrap(storage->p7_);
-    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,
-               typename Bound7UnwrapTraits::ForwardType)>
-               ::MakeItSo(storage->runnable_, CallbackForward(x1),
-                   CallbackForward(x2), CallbackForward(x3),
-                   CallbackForward(x4), CallbackForward(x5),
-                   CallbackForward(x6), CallbackForward(x7));
+    return InvokeHelperType::MakeItSo(
+        storage->runnable_,
+        Unwrappers::Unwrap(get<bound_indices>(storage->bound_args_))...,
+        CallbackForward(unbound_args)...);
   }
 };
 
@@ -1837,275 +360,52 @@ struct Invoker<7, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
 //
 // BoundArgsType contains the storage type for all the bound arguments by
 // (ab)using a function type.
-template <typename Runnable, typename RunType, typename BoundArgsType>
+template <typename Runnable, typename RunType, typename BoundArgList>
 struct BindState;
 
-template <typename Runnable, typename RunType>
-struct BindState<Runnable, RunType, void()> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef false_type IsWeakCall;
-  typedef Invoker<0, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-  explicit BindState(const Runnable& runnable)
-      : runnable_(runnable) {
-  }
-
-  RunnableType runnable_;
-
+template <typename Runnable,
+          typename R, typename... Args,
+          typename... BoundArgs>
+struct BindState<Runnable, R(Args...), TypeList<BoundArgs...>>
+    : public BindStateBase {
  private:
-  ~BindState() override {  }
+  using StorageType = BindState<Runnable, R(Args...), TypeList<BoundArgs...>>;
+  using RunnableType = Runnable;
 
-};
-
-template <typename Runnable, typename RunType, typename P1>
-struct BindState<Runnable, RunType, void(P1)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<1, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-
-  BindState(const Runnable& runnable, const P1& p1)
-      : runnable_(runnable),
-        p1_(p1) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
-
-template <typename Runnable, typename RunType, typename P1, typename P2>
-struct BindState<Runnable, RunType, void(P1, P2)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<2, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
-
-template <typename Runnable, typename RunType, typename P1, typename P2,
-    typename P3>
-struct BindState<Runnable, RunType, void(P1, P2, P3)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<3, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
-
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2),
-        p3_(p3) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-  P3 p3_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
+  // true_type if Runnable is a method invocation and the first bound argument
+  // is a WeakPtr.
+  using IsWeakCall =
+      IsWeakMethod<HasIsMethodTag<Runnable>::value, BoundArgs...>;
 
-template <typename Runnable, typename RunType, typename P1, typename P2,
-    typename P3, typename P4>
-struct BindState<Runnable, RunType, void(P1, P2, P3,
-    P4)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<4, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
+  using BoundIndices = MakeIndexSequence<sizeof...(BoundArgs)>;
+  using Unwrappers = TypeList<UnwrapTraits<BoundArgs>...>;
+  using UnboundForwardArgs = DropTypeListItem<
+      sizeof...(BoundArgs),
+      TypeList<typename CallbackParamTraits<Args>::ForwardType...>>;
+  using UnboundForwardRunType = MakeFunctionType<R, UnboundForwardArgs>;
 
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
-  typedef UnwrapTraits<P4> Bound4UnwrapTraits;
+  using InvokeHelperArgs = ConcatTypeLists<
+      TypeList<typename UnwrapTraits<BoundArgs>::ForwardType...>,
+      UnboundForwardArgs>;
+  using InvokeHelperType =
+      InvokeHelper<IsWeakCall::value, R, Runnable, InvokeHelperArgs>;
 
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3,
-      const P4& p4)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2),
-        p3_(p3),
-        p4_(p4) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-  P3 p3_;
-  P4 p4_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
-
-template <typename Runnable, typename RunType, typename P1, typename P2,
-    typename P3, typename P4, typename P5>
-struct BindState<Runnable, RunType, void(P1, P2, P3, P4,
-    P5)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<5, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
+  using UnboundArgs = DropTypeListItem<sizeof...(BoundArgs), TypeList<Args...>>;
 
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
-  typedef UnwrapTraits<P4> Bound4UnwrapTraits;
-  typedef UnwrapTraits<P5> Bound5UnwrapTraits;
-
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3,
-      const P4& p4, const P5& p5)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2),
-        p3_(p3),
-        p4_(p4),
-        p5_(p5) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-  P3 p3_;
-  P4 p4_;
-  P5 p5_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
-
-template <typename Runnable, typename RunType, typename P1, typename P2,
-    typename P3, typename P4, typename P5, typename P6>
-struct BindState<Runnable, RunType, void(P1, P2, P3, P4, P5,
-    P6)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<6, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
-  typedef UnwrapTraits<P4> Bound4UnwrapTraits;
-  typedef UnwrapTraits<P5> Bound5UnwrapTraits;
-  typedef UnwrapTraits<P6> Bound6UnwrapTraits;
-
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3,
-      const P4& p4, const P5& p5, const P6& p6)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2),
-        p3_(p3),
-        p4_(p4),
-        p5_(p5),
-        p6_(p6) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
-
-  RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-  P3 p3_;
-  P4 p4_;
-  P5 p5_;
-  P6 p6_;
-
- private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
-};
-
-template <typename Runnable, typename RunType, typename P1, typename P2,
-    typename P3, typename P4, typename P5, typename P6, typename P7>
-struct BindState<Runnable, RunType, void(P1, P2, P3, P4, P5, P6,
-    P7)> : public BindStateBase {
-  typedef Runnable RunnableType;
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-  typedef Invoker<7, BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-  // Convenience typedefs for bound argument types.
-  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
-  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
-  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
-  typedef UnwrapTraits<P4> Bound4UnwrapTraits;
-  typedef UnwrapTraits<P5> Bound5UnwrapTraits;
-  typedef UnwrapTraits<P6> Bound6UnwrapTraits;
-  typedef UnwrapTraits<P7> Bound7UnwrapTraits;
+ public:
+  using InvokerType = Invoker<BoundIndices, StorageType, Unwrappers,
+                              InvokeHelperType, UnboundForwardRunType>;
+  using UnboundRunType = MakeFunctionType<R, UnboundArgs>;
 
-  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3,
-      const P4& p4, const P5& p5, const P6& p6, const P7& p7)
-      : runnable_(runnable),
-        p1_(p1),
-        p2_(p2),
-        p3_(p3),
-        p4_(p4),
-        p5_(p5),
-        p6_(p6),
-        p7_(p7) {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-  }
+  BindState(const Runnable& runnable, const BoundArgs&... bound_args)
+      : runnable_(runnable), ref_(bound_args...), bound_args_(bound_args...) {}
 
   RunnableType runnable_;
-  P1 p1_;
-  P2 p2_;
-  P3 p3_;
-  P4 p4_;
-  P5 p5_;
-  P6 p6_;
-  P7 p7_;
+  MaybeScopedRefPtr<HasIsMethodTag<Runnable>::value, BoundArgs...> ref_;
+  Tuple<BoundArgs...> bound_args_;
 
  private:
-  ~BindState() override {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
-      P1>::Release(p1_);  }
-
+  ~BindState() override {}
 };
 
 }  // namespace internal
diff --git a/base/bind_internal.h.pump b/base/bind_internal.h.pump
deleted file mode 100644
index 0ed3ca2..0000000
--- a/base/bind_internal.h.pump
+++ /dev/null
@@ -1,516 +0,0 @@
-$$ This is a pump file for generating file templates.  Pump is a python
-$$ script that is part of the Google Test suite of utilities.  Description
-$$ can be found here:
-$$
-$$ http://code.google.com/p/googletest/wiki/PumpManual
-$$
-
-$$ See comment for MAX_ARITY in base/bind.h.pump.
-$var MAX_ARITY = 7
-$range ARITY 0..MAX_ARITY
-
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_BIND_INTERNAL_H_
-#define BASE_BIND_INTERNAL_H_
-
-#include "base/bind_helpers.h"
-#include "base/callback_internal.h"
-#include "base/memory/raw_scoped_refptr_mismatch_checker.h"
-#include "base/memory/weak_ptr.h"
-#include "base/template_util.h"
-#include "build/build_config.h"
-
-#if defined(OS_WIN)
-#include "base/bind_internal_win.h"
-#endif
-
-namespace base {
-namespace 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.
-//  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.
-//  FunctorTraits<> -- Type traits used determine the correct RunType and
-//                     RunnableType for a Functor.  This is where function
-//                     signature adapters are applied.
-//  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.
-//  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.
-
-// HasNonConstReferenceParam selects true_type when any of the parameters in
-// |Sig| is a non-const reference.
-// Implementation note: This non-specialized case handles zero-arity case only.
-// Non-zero-arity cases should be handled by the specialization below.
-template <typename Sig>
-struct HasNonConstReferenceParam : false_type {};
-
-// Implementation note: Select true_type if the first parameter is a non-const
-// reference.  Otherwise, skip the first parameter and check rest of parameters
-// recursively.
-template <typename R, typename T, typename... Args>
-struct HasNonConstReferenceParam<R(T, Args...)>
-    : SelectType<is_non_const_reference<T>::value,
-                 true_type,
-                 HasNonConstReferenceParam<R(Args...)>>::Type {};
-
-// HasRefCountedTypeAsRawPtr selects true_type when any of the |Args| is a raw
-// pointer to a RefCounted type.
-// Implementation note: This non-specialized case handles zero-arity case only.
-// Non-zero-arity cases should be handled by the specialization below.
-template <typename... Args>
-struct HasRefCountedTypeAsRawPtr : false_type {};
-
-// Implementation note: Select true_type if the first parameter is a raw pointer
-// to a RefCounted type. Otherwise, skip the first parameter and check rest of
-// parameters recursively.
-template <typename T, typename... Args>
-struct HasRefCountedTypeAsRawPtr<T, Args...>
-    : SelectType<NeedsScopedRefptrButGetsRawPtr<T>::value,
-                 true_type,
-                 HasRefCountedTypeAsRawPtr<Args...>>::Type {};
-
-// BindsArrayToFirstArg selects true_type when |is_method| is true and the first
-// item of |Args| is an array type.
-// Implementation note: This non-specialized case handles !is_method case and
-// zero-arity case only.  Other cases should be handled by the specialization
-// below.
-template <bool is_method, typename... Args>
-struct BindsArrayToFirstArg : false_type {};
-
-template <typename T, typename... Args>
-struct BindsArrayToFirstArg<true, T, Args...> : is_array<T> {};
-
-// HasRefCountedParamAsRawPtr is the same to HasRefCountedTypeAsRawPtr except
-// when |is_method| is true HasRefCountedParamAsRawPtr skips the first argument.
-// Implementation note: This non-specialized case handles !is_method case and
-// zero-arity case only.  Other cases should be handled by the specialization
-// below.
-template <bool is_method, typename... Args>
-struct HasRefCountedParamAsRawPtr : HasRefCountedTypeAsRawPtr<Args...> {};
-
-template <typename T, typename... Args>
-struct HasRefCountedParamAsRawPtr<true, T, Args...>
-    : HasRefCountedTypeAsRawPtr<Args...> {};
-
-// 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.
-template <typename R, typename... Args>
-class RunnableAdapter<R(*)(Args...)> {
- public:
-  typedef R (RunType)(Args...);
-
-  explicit RunnableAdapter(R(*function)(Args...))
-      : function_(function) {
-  }
-
-  R Run(typename CallbackParamTraits<Args>::ForwardType... args) {
-    return function_(CallbackForward(args)...);
-  }
-
- private:
-  R (*function_)(Args...);
-};
-
-// Method.
-template <typename R, typename T, typename... Args>
-class RunnableAdapter<R(T::*)(Args...)> {
- public:
-  typedef R (RunType)(T*, Args...);
-  typedef true_type IsMethod;
-
-  explicit RunnableAdapter(R(T::*method)(Args...))
-      : method_(method) {
-  }
-
-  R Run(T* object, typename CallbackParamTraits<Args>::ForwardType... args) {
-    return (object->*method_)(CallbackForward(args)...);
-  }
-
- private:
-  R (T::*method_)(Args...);
-};
-
-// Const Method.
-template <typename R, typename T, typename... Args>
-class RunnableAdapter<R(T::*)(Args...) const> {
- public:
-  typedef R (RunType)(const T*, Args...);
-  typedef true_type IsMethod;
-
-  explicit RunnableAdapter(R(T::*method)(Args...) const)
-      : method_(method) {
-  }
-
-  R Run(const T* object,
-        typename CallbackParamTraits<Args>::ForwardType... args) {
-    return (object->*method_)(CallbackForward(args)...);
-  }
-
- private:
-  R (T::*method_)(Args...) const;
-};
-
-// TODO(tzik): Remove FunctionTraits after we finish removing bind.pump.
-// FunctionTraits<>
-//
-// Breaks a function signature apart into typedefs for easier introspection.
-template <typename Sig>
-struct FunctionTraits;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <typename R[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-struct FunctionTraits<R($for ARG , [[A$(ARG)]])> {
-  typedef R ReturnType;
-$for ARG [[
-
-  typedef A$(ARG) A$(ARG)Type;
-]]
-
-};
-
-]]
-
-
-// ForceVoidReturn<>
-//
-// Set of templates that support forcing the function return type to void.
-template <typename Sig>
-struct ForceVoidReturn;
-
-template <typename R, typename... Args>
-struct ForceVoidReturn<R(Args...)> {
-  typedef void(RunType)(Args...);
-};
-
-
-// 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, typename... Args>
-struct InvokeHelper<false, ReturnType, Runnable,
-    void(Args...)>  {
-  static ReturnType MakeItSo(Runnable runnable, Args... args) {
-    return runnable.Run(CallbackForward(args)...);
-  }
-};
-
-template <typename Runnable, typename... Args>
-struct InvokeHelper<false, void, Runnable, void(Args...)>  {
-  static void MakeItSo(Runnable runnable, Args... args) {
-    runnable.Run(CallbackForward(args)...);
-  }
-};
-
-template <typename Runnable, typename BoundWeakPtr, typename... Args>
-struct InvokeHelper<true, void, Runnable, void(BoundWeakPtr, Args...)>  {
-  static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr, Args... args) {
-    if (!weak_ptr.get()) {
-      return;
-    }
-    runnable.Run(weak_ptr.get(), CallbackForward(args)...);
-  }
-};
-
-#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;
-
-$for ARITY [[
-
-$$ Number of bound arguments.
-$range BOUND 0..ARITY
-$for BOUND [[
-
-$var UNBOUND = ARITY - BOUND
-$range ARG 1..ARITY
-$range BOUND_ARG 1..BOUND
-$range UNBOUND_ARG (ARITY - UNBOUND + 1)..ARITY
-
-// Arity $(ARITY) -> $(UNBOUND).
-template <typename StorageType, typename R[[]]
-$if ARITY > 0 [[,]][[]]
-$for ARG , [[typename X$(ARG)]]>
-struct Invoker<$(BOUND), StorageType, R($for ARG , [[X$(ARG)]])> {
-  typedef R(RunType)(BindStateBase*[[]]
-$if UNBOUND != 0 [[, ]]
-$for UNBOUND_ARG , [[typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType]]);
-
-  typedef R(UnboundRunType)($for UNBOUND_ARG , [[X$(UNBOUND_ARG)]]);
-
-  static R Run(BindStateBase* base[[]]
-$if UNBOUND != 0 [[, ]][[]]
-$for UNBOUND_ARG , [[
-typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType x$(UNBOUND_ARG)
-]][[]]
-) {
-    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.
-$for BOUND_ARG
-[[
-
-    typedef typename StorageType::Bound$(BOUND_ARG)UnwrapTraits Bound$(BOUND_ARG)UnwrapTraits;
-]]
-
-
-$for BOUND_ARG
-[[
-
-    typename Bound$(BOUND_ARG)UnwrapTraits::ForwardType x$(BOUND_ARG) =
-        Bound$(BOUND_ARG)UnwrapTraits::Unwrap(storage->p$(BOUND_ARG)_);
-]]
-
-    return InvokeHelper<StorageType::IsWeakCall::value, R,
-           typename StorageType::RunnableType,
-           void(
-$for BOUND_ARG , [[
-typename Bound$(BOUND_ARG)UnwrapTraits::ForwardType
-]]
-
-$if UNBOUND > 0 [[$if BOUND > 0 [[, ]]]][[]]
-
-$for UNBOUND_ARG , [[
-typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType x$(UNBOUND_ARG)
-]]
-)>
-               ::MakeItSo(storage->runnable_
-$if ARITY > 0[[, ]] $for ARG , [[CallbackForward(x$(ARG))]]);
-  }
-};
-
-]] $$ for BOUND
-]] $$ for ARITY
-
-
-// BindState<>
-//
-// This stores all the state passed into Bind() and is also where most
-// of the template resolution magic occurs.
-//
-// Runnable is the functor we are binding arguments to.
-// RunType is type of the Run() function that the Invoker<> should use.
-// Normally, this is the same as the RunType of the Runnable, but it can
-// be different if an adapter like IgnoreResult() has been used.
-//
-// BoundArgsType contains the storage type for all the bound arguments by
-// (ab)using a function type.
-template <typename Runnable, typename RunType, typename BoundArgsType>
-struct BindState;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <typename Runnable, typename RunType[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename P$(ARG)]]>
-struct BindState<Runnable, RunType, void($for ARG , [[P$(ARG)]])> : public BindStateBase {
-  typedef Runnable RunnableType;
-
-$if ARITY > 0 [[
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-]] $else [[
-  typedef false_type IsWeakCall;
-]]
-
-  typedef Invoker<$(ARITY), BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-$if ARITY > 0 [[
-
-  // Convenience typedefs for bound argument types.
-
-$for ARG [[
-  typedef UnwrapTraits<P$(ARG)> Bound$(ARG)UnwrapTraits;
-
-]]  $$ for ARG
-
-
-]]  $$ if ARITY > 0
-
-$$ The extra [[ ]] is needed to massage spacing. Silly pump.py.
-[[  ]]$if ARITY == 0 [[explicit ]]BindState(const Runnable& runnable
-$if ARITY > 0 [[, ]] $for ARG , [[const P$(ARG)& p$(ARG)]])
-      : runnable_(runnable)[[]]
-$if ARITY == 0 [[
- {
-
-]] $else [[
-, $for ARG , [[
-
-        p$(ARG)_(p$(ARG))
-]] {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-
-]]
-  }
-
-  RunnableType runnable_;
-
-$for ARG [[
-  P$(ARG) p$(ARG)_;
-
-]]
-
- private:
-  ~BindState() override {
-$if ARITY > 0 [[
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::Release(p1_);
-]]
-  }
-
-};
-
-]] $$ for ARITY
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_BIND_INTERNAL_H_
diff --git a/base/bind_unittest.nc b/base/bind_unittest.nc
index 33b5f5c..2596386 100644
--- a/base/bind_unittest.nc
+++ b/base/bind_unittest.nc
@@ -190,7 +190,7 @@ void WontCompile() {
   weak_ptr_with_non_void_return_type.Run();
 }
 
-#elif defined(NCTEST_DISALLOW_ASSIGN_DIFFERENT_TYPES)  // [r"fatal error: no viable conversion from 'Callback<typename internal::BindState<typename internal::FunctorTraits<void \(\*\)\(int\)>::RunnableType, typename internal::FunctorTraits<void \(\*\)\(int\)>::RunType, void \(\)>::UnboundRunType>' to 'Callback<void \(\)>'"]
+#elif defined(NCTEST_DISALLOW_ASSIGN_DIFFERENT_TYPES)  // [r"fatal error: no viable conversion from 'Callback<typename internal::BindState<typename internal::FunctorTraits<void \(\*\)\(int\)>::RunnableType, typename internal::FunctorTraits<void \(\*\)\(int\)>::RunType, internal::TypeList<> >::UnboundRunType>' to 'Callback<void \(\)>'"]
 
 // Bind result cannot be assigned to Callbacks with a mismatching type.
 void WontCompile() {