Remove unbound base::Bind overload

This CL removes a base::Bind overload without bound arguments.
The difference to generic base::Bind is the type check for the bound
Runnable: the generic one ensures any argument of the Runnable
is not non-const reference, OTHT, the overload being removed checks
nothing.

Where, comments and tests asserts any *bound* argument should not be
non-const reference, so the generic one has been checked excessively.
This CL loosen the type check to match the requirement, and then
the overloaded base::Bind is no longer needed.

BUG=

Review URL: https://codereview.chromium.org/1512833002

Cr-Commit-Position: refs/heads/master@{#365988}

base/bind.h

@@ -47,22 +47,6 @@
 
 namespace base {
 
-template <typename Functor>
-base::Callback<
-    typename internal::BindState<
-        typename internal::FunctorTraits<Functor>::RunnableType,
-        typename internal::FunctorTraits<Functor>::RunType>::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> BindState;
-
-  return Callback<typename BindState::UnboundRunType>(
-      new BindState(internal::MakeRunnable(functor)));
-}
-
 template <typename Functor, typename... Args>
 base::Callback<
     typename internal::BindState<
@@ -80,12 +64,16 @@ Bind(Functor functor, const Args&... args) {
   // functor is going to interpret the argument as.
   typedef typename RunnableType::RunType BoundRunType;
 
+  using BoundArgs =
+      internal::TakeTypeListItem<sizeof...(Args),
+                                 internal::ExtractArgs<BoundRunType>>;
+
   // Do not allow binding a non-const reference parameter. Non-const reference
   // parameters are disallowed by the Google style guide.  Also, binding a
   // non-const reference parameter can make for subtle bugs because the
   // invoked function will receive a reference to the stored copy of the
   // argument and not the original.
-  static_assert(!internal::HasNonConstReferenceParam<BoundRunType>::value,
+  static_assert(!internal::HasNonConstReferenceItem<BoundArgs>::value,
                 "do not bind functions with nonconst ref");
 
   const bool is_method = internal::HasIsMethodTag<RunnableType>::value;

base/bind_helpers.h

@@ -527,6 +527,31 @@ struct DropTypeListItemImpl<0, TypeList<>> {
 template <size_t n, typename List>
 using DropTypeListItem = typename DropTypeListItemImpl<n, List>::Type;
 
+// Used for TakeTypeListItem implementation.
+template <size_t n, typename List, typename... Accum>
+struct TakeTypeListItemImpl;
+
+// Do not use enable_if and SFINAE here to avoid MSVC2013 compile failure.
+template <size_t n, typename T, typename... List, typename... Accum>
+struct TakeTypeListItemImpl<n, TypeList<T, List...>, Accum...>
+    : TakeTypeListItemImpl<n - 1, TypeList<List...>, Accum..., T> {};
+
+template <typename T, typename... List, typename... Accum>
+struct TakeTypeListItemImpl<0, TypeList<T, List...>, Accum...> {
+  using Type = TypeList<Accum...>;
+};
+
+template <typename... Accum>
+struct TakeTypeListItemImpl<0, TypeList<>, Accum...> {
+  using Type = TypeList<Accum...>;
+};
+
+// A type-level function that takes first |n| list item from given TypeList.
+// E.g. TakeTypeListItem<3, TypeList<A, B, C, D>> is evaluated to
+// TypeList<A, B, C>.
+template <size_t n, typename List>
+using TakeTypeListItem = typename TakeTypeListItemImpl<n, List>::Type;
+
 // Used for ConcatTypeLists implementation.
 template <typename List1, typename List2>
 struct ConcatTypeListsImpl;
@@ -554,6 +579,20 @@ struct MakeFunctionTypeImpl<R, TypeList<Args...>> {
 template <typename R, typename ArgList>
 using MakeFunctionType = typename MakeFunctionTypeImpl<R, ArgList>::Type;
 
+// Used for ExtractArgs.
+template <typename Signature>
+struct ExtractArgsImpl;
+
+template <typename R, typename... Args>
+struct ExtractArgsImpl<R(Args...)> {
+  using Type = TypeList<Args...>;
+};
+
+// A type-level function that extracts function arguments into a TypeList.
+// E.g. ExtractArgs<R(A, B, C)> is evaluated to TypeList<A, B, C>.
+template <typename Signature>
+using ExtractArgs = typename ExtractArgsImpl<Signature>::Type;
+
 }  // namespace internal
 
 template <typename T>

base/bind_internal.h

@@ -65,17 +65,17 @@ namespace internal {
 // |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 {};
+template <typename List>
+struct HasNonConstReferenceItem : 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...)>
+template <typename T, typename... Args>
+struct HasNonConstReferenceItem<TypeList<T, Args...>>
     : std::conditional<is_non_const_reference<T>::value,
                        true_type,
-                       HasNonConstReferenceParam<R(Args...)>>::type {};
+                       HasNonConstReferenceItem<TypeList<Args...>>>::type {};
 
 // HasRefCountedTypeAsRawPtr selects true_type when any of the |Args| is a raw
 // pointer to a RefCounted type.

base/bind_unittest.cc

@@ -162,9 +162,10 @@ T PolymorphicIdentity(T t) {
   return t;
 }
 
-template <typename T>
-void VoidPolymorphic1(T t) {
-}
+template <typename... Ts>
+struct VoidPolymorphic {
+  static void Run(Ts... t) {}
+};
 
 int Identity(int n) {
   return n;
@@ -499,17 +500,20 @@ TEST_F(BindTest, ArgumentBinding) {
 //   - Unbound sized array.
 //   - Unbound array-of-arrays.
 TEST_F(BindTest, UnboundArgumentTypeSupport) {
-  Callback<void(int)> unbound_value_cb = Bind(&VoidPolymorphic1<int>);
-  Callback<void(int*)> unbound_pointer_cb = Bind(&VoidPolymorphic1<int*>);
-  Callback<void(int&)> unbound_ref_cb = Bind(&VoidPolymorphic1<int&>);
+  Callback<void(int)> unbound_value_cb = Bind(&VoidPolymorphic<int>::Run);
+  Callback<void(int*)> unbound_pointer_cb = Bind(&VoidPolymorphic<int*>::Run);
+  Callback<void(int&)> unbound_ref_cb = Bind(&VoidPolymorphic<int&>::Run);
   Callback<void(const int&)> unbound_const_ref_cb =
-      Bind(&VoidPolymorphic1<const int&>);
+      Bind(&VoidPolymorphic<const int&>::Run);
   Callback<void(int[])> unbound_unsized_array_cb =
-      Bind(&VoidPolymorphic1<int[]>);
+      Bind(&VoidPolymorphic<int[]>::Run);
   Callback<void(int[2])> unbound_sized_array_cb =
-      Bind(&VoidPolymorphic1<int[2]>);
+      Bind(&VoidPolymorphic<int[2]>::Run);
   Callback<void(int[][2])> unbound_array_of_arrays_cb =
-      Bind(&VoidPolymorphic1<int[][2]>);
+      Bind(&VoidPolymorphic<int[][2]>::Run);
+
+  Callback<void(int&)> unbound_ref_with_bound_arg =
+      Bind(&VoidPolymorphic<int, int&>::Run, 1);
 }
 
 // Function with unbound reference parameter.
@@ -810,14 +814,14 @@ TEST_F(BindTest, ArgumentCopies) {
   CopyCounter counter(&copies, &assigns);
 
   Callback<void(void)> copy_cb =
-      Bind(&VoidPolymorphic1<CopyCounter>, counter);
+      Bind(&VoidPolymorphic<CopyCounter>::Run, counter);
   EXPECT_GE(1, copies);
   EXPECT_EQ(0, assigns);
 
   copies = 0;
   assigns = 0;
   Callback<void(CopyCounter)> forward_cb =
-      Bind(&VoidPolymorphic1<CopyCounter>);
+      Bind(&VoidPolymorphic<CopyCounter>::Run);
   forward_cb.Run(counter);
   EXPECT_GE(1, copies);
   EXPECT_EQ(0, assigns);
@@ -826,7 +830,7 @@ TEST_F(BindTest, ArgumentCopies) {
   assigns = 0;
   DerivedCopyCounter derived(&copies, &assigns);
   Callback<void(CopyCounter)> coerce_cb =
-      Bind(&VoidPolymorphic1<CopyCounter>);
+      Bind(&VoidPolymorphic<CopyCounter>::Run);
   coerce_cb.Run(CopyCounter(derived));
   EXPECT_GE(2, copies);
   EXPECT_EQ(0, assigns);