From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <mattatobin@localhost.localdomain>
Date: Fri, 2 Feb 2018 04:16:08 -0500
Subject: Add m-esr52 at 52.6.0

---
 mfbt/TypeTraits.h | 1262 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1262 insertions(+)
 create mode 100644 mfbt/TypeTraits.h

(limited to 'mfbt/TypeTraits.h')

diff --git a/mfbt/TypeTraits.h b/mfbt/TypeTraits.h
new file mode 100644
index 000000000..084f608ca
--- /dev/null
+++ b/mfbt/TypeTraits.h
@@ -0,0 +1,1262 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Template-based metaprogramming and type-testing facilities. */
+
+#ifndef mozilla_TypeTraits_h
+#define mozilla_TypeTraits_h
+
+#include "mozilla/Types.h"
+
+/*
+ * These traits are approximate copies of the traits and semantics from C++11's
+ * <type_traits> header.  Don't add traits not in that header!  When all
+ * platforms provide that header, we can convert all users and remove this one.
+ */
+
+#include <wchar.h>
+
+namespace mozilla {
+
+/* Forward declarations. */
+
+template<typename> struct RemoveCV;
+template<typename> struct AddRvalueReference;
+
+/* 20.2.4 Function template declval [declval] */
+
+/**
+ * DeclVal simplifies the definition of expressions which occur as unevaluated
+ * operands. It converts T to a reference type, making it possible to use in
+ * decltype expressions even if T does not have a default constructor, e.g.:
+ * decltype(DeclVal<TWithNoDefaultConstructor>().foo())
+ */
+template<typename T>
+typename AddRvalueReference<T>::Type DeclVal();
+
+/* 20.9.3 Helper classes [meta.help] */
+
+/**
+ * Helper class used as a base for various type traits, exposed publicly
+ * because <type_traits> exposes it as well.
+ */
+template<typename T, T Value>
+struct IntegralConstant
+{
+  static const T value = Value;
+  typedef T ValueType;
+  typedef IntegralConstant<T, Value> Type;
+};
+
+/** Convenient aliases. */
+typedef IntegralConstant<bool, true> TrueType;
+typedef IntegralConstant<bool, false> FalseType;
+
+/* 20.9.4 Unary type traits [meta.unary] */
+
+/* 20.9.4.1 Primary type categories [meta.unary.cat] */
+
+namespace detail {
+
+template<typename T>
+struct IsVoidHelper : FalseType {};
+
+template<>
+struct IsVoidHelper<void> : TrueType {};
+
+} // namespace detail
+
+/**
+ * IsVoid determines whether a type is void.
+ *
+ * mozilla::IsVoid<int>::value is false;
+ * mozilla::IsVoid<void>::value is true;
+ * mozilla::IsVoid<void*>::value is false;
+ * mozilla::IsVoid<volatile void>::value is true.
+ */
+template<typename T>
+struct IsVoid : detail::IsVoidHelper<typename RemoveCV<T>::Type> {};
+
+namespace detail {
+
+template <typename T>
+struct IsIntegralHelper : FalseType {};
+
+template<> struct IsIntegralHelper<char>               : TrueType {};
+template<> struct IsIntegralHelper<signed char>        : TrueType {};
+template<> struct IsIntegralHelper<unsigned char>      : TrueType {};
+template<> struct IsIntegralHelper<short>              : TrueType {};
+template<> struct IsIntegralHelper<unsigned short>     : TrueType {};
+template<> struct IsIntegralHelper<int>                : TrueType {};
+template<> struct IsIntegralHelper<unsigned int>       : TrueType {};
+template<> struct IsIntegralHelper<long>               : TrueType {};
+template<> struct IsIntegralHelper<unsigned long>      : TrueType {};
+template<> struct IsIntegralHelper<long long>          : TrueType {};
+template<> struct IsIntegralHelper<unsigned long long> : TrueType {};
+template<> struct IsIntegralHelper<bool>               : TrueType {};
+template<> struct IsIntegralHelper<wchar_t>            : TrueType {};
+template<> struct IsIntegralHelper<char16_t>           : TrueType {};
+
+} /* namespace detail */
+
+/**
+ * IsIntegral determines whether a type is an integral type.
+ *
+ * mozilla::IsIntegral<int>::value is true;
+ * mozilla::IsIntegral<unsigned short>::value is true;
+ * mozilla::IsIntegral<const long>::value is true;
+ * mozilla::IsIntegral<int*>::value is false;
+ * mozilla::IsIntegral<double>::value is false;
+ */
+template<typename T>
+struct IsIntegral : detail::IsIntegralHelper<typename RemoveCV<T>::Type>
+{};
+
+template<typename T, typename U>
+struct IsSame;
+
+namespace detail {
+
+template<typename T>
+struct IsFloatingPointHelper
+  : IntegralConstant<bool,
+                     IsSame<T, float>::value ||
+                     IsSame<T, double>::value ||
+                     IsSame<T, long double>::value>
+{};
+
+} // namespace detail
+
+/**
+ * IsFloatingPoint determines whether a type is a floating point type (float,
+ * double, long double).
+ *
+ * mozilla::IsFloatingPoint<int>::value is false;
+ * mozilla::IsFloatingPoint<const float>::value is true;
+ * mozilla::IsFloatingPoint<long double>::value is true;
+ * mozilla::IsFloatingPoint<double*>::value is false.
+ */
+template<typename T>
+struct IsFloatingPoint
+  : detail::IsFloatingPointHelper<typename RemoveCV<T>::Type>
+{};
+
+namespace detail {
+
+template<typename T>
+struct IsArrayHelper : FalseType {};
+
+template<typename T, decltype(sizeof(1)) N>
+struct IsArrayHelper<T[N]> : TrueType {};
+
+template<typename T>
+struct IsArrayHelper<T[]> : TrueType {};
+
+} // namespace detail
+
+/**
+ * IsArray determines whether a type is an array type, of known or unknown
+ * length.
+ *
+ * mozilla::IsArray<int>::value is false;
+ * mozilla::IsArray<int[]>::value is true;
+ * mozilla::IsArray<int[5]>::value is true.
+ */
+template<typename T>
+struct IsArray : detail::IsArrayHelper<typename RemoveCV<T>::Type>
+{};
+
+namespace detail {
+
+template<typename T>
+struct IsFunPtr;
+
+template<typename>
+struct IsFunPtr
+  : public FalseType
+{};
+
+template<typename Result, typename... ArgTypes>
+struct IsFunPtr<Result(*)(ArgTypes...)>
+  : public TrueType
+{};
+
+}; // namespace detail
+
+/**
+ * IsFunction determines whether a type is a function type. Function pointers
+ * don't qualify here--only the type of an actual function symbol. We do not
+ * correctly handle varags function types because of a bug in MSVC.
+ *
+ * Given the function:
+ *   void f(int) {}
+ *
+ * mozilla::IsFunction<void(int)> is true;
+ * mozilla::IsFunction<void(*)(int)> is false;
+ * mozilla::IsFunction<decltype(f)> is true.
+ */
+template<typename T>
+struct IsFunction
+  : public detail::IsFunPtr<typename RemoveCV<T>::Type *>
+{};
+
+namespace detail {
+
+template<typename T>
+struct IsPointerHelper : FalseType {};
+
+template<typename T>
+struct IsPointerHelper<T*> : TrueType {};
+
+} // namespace detail
+
+/**
+ * IsPointer determines whether a type is a possibly-CV-qualified pointer type
+ * (but not a pointer-to-member type).
+ *
+ * mozilla::IsPointer<struct S*>::value is true;
+ * mozilla::IsPointer<int*>::value is true;
+ * mozilla::IsPointer<int**>::value is true;
+ * mozilla::IsPointer<const int*>::value is true;
+ * mozilla::IsPointer<int* const>::value is true;
+ * mozilla::IsPointer<int* volatile>::value is true;
+ * mozilla::IsPointer<void (*)(void)>::value is true;
+ * mozilla::IsPointer<int>::value is false;
+ * mozilla::IsPointer<struct S>::value is false.
+ * mozilla::IsPointer<int(struct S::*)>::value is false
+ */
+template<typename T>
+struct IsPointer : detail::IsPointerHelper<typename RemoveCV<T>::Type>
+{};
+
+/**
+ * IsLvalueReference determines whether a type is an lvalue reference.
+ *
+ * mozilla::IsLvalueReference<struct S*>::value is false;
+ * mozilla::IsLvalueReference<int**>::value is false;
+ * mozilla::IsLvalueReference<void (*)(void)>::value is false;
+ * mozilla::IsLvalueReference<int>::value is false;
+ * mozilla::IsLvalueReference<struct S>::value is false;
+ * mozilla::IsLvalueReference<struct S*&>::value is true;
+ * mozilla::IsLvalueReference<struct S&&>::value is false.
+ */
+template<typename T>
+struct IsLvalueReference : FalseType {};
+
+template<typename T>
+struct IsLvalueReference<T&> : TrueType {};
+
+/**
+ * IsRvalueReference determines whether a type is an rvalue reference.
+ *
+ * mozilla::IsRvalueReference<struct S*>::value is false;
+ * mozilla::IsRvalueReference<int**>::value is false;
+ * mozilla::IsRvalueReference<void (*)(void)>::value is false;
+ * mozilla::IsRvalueReference<int>::value is false;
+ * mozilla::IsRvalueReference<struct S>::value is false;
+ * mozilla::IsRvalueReference<struct S*&>::value is false;
+ * mozilla::IsRvalueReference<struct S&&>::value is true.
+ */
+template<typename T>
+struct IsRvalueReference : FalseType {};
+
+template<typename T>
+struct IsRvalueReference<T&&> : TrueType {};
+
+namespace detail {
+
+// __is_enum is a supported extension across all of our supported compilers.
+template<typename T>
+struct IsEnumHelper
+  : IntegralConstant<bool, __is_enum(T)>
+{};
+
+} // namespace detail
+
+/**
+ * IsEnum determines whether a type is an enum type.
+ *
+ * mozilla::IsEnum<enum S>::value is true;
+ * mozilla::IsEnum<enum S*>::value is false;
+ * mozilla::IsEnum<int>::value is false;
+ */
+template<typename T>
+struct IsEnum
+  : detail::IsEnumHelper<typename RemoveCV<T>::Type>
+{};
+
+namespace detail {
+
+// __is_class is a supported extension across all of our supported compilers:
+// http://llvm.org/releases/3.0/docs/ClangReleaseNotes.html
+// http://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Type-Traits.html#Type-Traits
+// http://msdn.microsoft.com/en-us/library/ms177194%28v=vs.100%29.aspx
+template<typename T>
+struct IsClassHelper
+  : IntegralConstant<bool, __is_class(T)>
+{};
+
+} // namespace detail
+
+/**
+ * IsClass determines whether a type is a class type (but not a union).
+ *
+ * struct S {};
+ * union U {};
+ * mozilla::IsClass<int>::value is false;
+ * mozilla::IsClass<const S>::value is true;
+ * mozilla::IsClass<U>::value is false;
+ */
+template<typename T>
+struct IsClass
+  : detail::IsClassHelper<typename RemoveCV<T>::Type>
+{};
+
+/* 20.9.4.2 Composite type traits [meta.unary.comp] */
+
+/**
+ * IsReference determines whether a type is an lvalue or rvalue reference.
+ *
+ * mozilla::IsReference<struct S*>::value is false;
+ * mozilla::IsReference<int**>::value is false;
+ * mozilla::IsReference<int&>::value is true;
+ * mozilla::IsReference<void (*)(void)>::value is false;
+ * mozilla::IsReference<const int&>::value is true;
+ * mozilla::IsReference<int>::value is false;
+ * mozilla::IsReference<struct S>::value is false;
+ * mozilla::IsReference<struct S&>::value is true;
+ * mozilla::IsReference<struct S*&>::value is true;
+ * mozilla::IsReference<struct S&&>::value is true.
+ */
+template<typename T>
+struct IsReference
+  : IntegralConstant<bool,
+                     IsLvalueReference<T>::value || IsRvalueReference<T>::value>
+{};
+
+/**
+ * IsArithmetic determines whether a type is arithmetic.  A type is arithmetic
+ * iff it is an integral type or a floating point type.
+ *
+ * mozilla::IsArithmetic<int>::value is true;
+ * mozilla::IsArithmetic<double>::value is true;
+ * mozilla::IsArithmetic<long double*>::value is false.
+ */
+template<typename T>
+struct IsArithmetic
+  : IntegralConstant<bool, IsIntegral<T>::value || IsFloatingPoint<T>::value>
+{};
+
+namespace detail {
+
+template<typename T>
+struct IsMemberPointerHelper : FalseType {};
+
+template<typename T, typename U>
+struct IsMemberPointerHelper<T U::*> : TrueType {};
+
+} // namespace detail
+
+/**
+ * IsMemberPointer determines whether a type is pointer to non-static member
+ * object or a pointer to non-static member function.
+ *
+ * mozilla::IsMemberPointer<int(cls::*)>::value is true
+ * mozilla::IsMemberPointer<int*>::value is false
+ */
+template<typename T>
+struct IsMemberPointer
+  : detail::IsMemberPointerHelper<typename RemoveCV<T>::Type>
+{};
+
+/**
+ * IsScalar determines whether a type is a scalar type.
+ *
+ * mozilla::IsScalar<int>::value is true
+ * mozilla::IsScalar<int*>::value is true
+ * mozilla::IsScalar<cls>::value is false
+ */
+template<typename T>
+struct IsScalar
+  : IntegralConstant<bool, IsArithmetic<T>::value || IsEnum<T>::value ||
+                     IsPointer<T>::value || IsMemberPointer<T>::value>
+{};
+
+/* 20.9.4.3 Type properties [meta.unary.prop] */
+
+/**
+ * IsConst determines whether a type is const or not.
+ *
+ * mozilla::IsConst<int>::value is false;
+ * mozilla::IsConst<void* const>::value is true;
+ * mozilla::IsConst<const char*>::value is false.
+ */
+template<typename T>
+struct IsConst : FalseType {};
+
+template<typename T>
+struct IsConst<const T> : TrueType {};
+
+/**
+ * IsVolatile determines whether a type is volatile or not.
+ *
+ * mozilla::IsVolatile<int>::value is false;
+ * mozilla::IsVolatile<void* volatile>::value is true;
+ * mozilla::IsVolatile<volatile char*>::value is false.
+ */
+template<typename T>
+struct IsVolatile : FalseType {};
+
+template<typename T>
+struct IsVolatile<volatile T> : TrueType {};
+
+/**
+ * Traits class for identifying POD types.  Until C++11 there's no automatic
+ * way to detect PODs, so for the moment this is done manually.  Users may
+ * define specializations of this class that inherit from mozilla::TrueType and
+ * mozilla::FalseType (or equivalently mozilla::IntegralConstant<bool, true or
+ * false>, or conveniently from mozilla::IsPod for composite types) as needed to
+ * ensure correct IsPod behavior.
+ */
+template<typename T>
+struct IsPod : public FalseType {};
+
+template<> struct IsPod<char>               : TrueType {};
+template<> struct IsPod<signed char>        : TrueType {};
+template<> struct IsPod<unsigned char>      : TrueType {};
+template<> struct IsPod<short>              : TrueType {};
+template<> struct IsPod<unsigned short>     : TrueType {};
+template<> struct IsPod<int>                : TrueType {};
+template<> struct IsPod<unsigned int>       : TrueType {};
+template<> struct IsPod<long>               : TrueType {};
+template<> struct IsPod<unsigned long>      : TrueType {};
+template<> struct IsPod<long long>          : TrueType {};
+template<> struct IsPod<unsigned long long> : TrueType {};
+template<> struct IsPod<bool>               : TrueType {};
+template<> struct IsPod<float>              : TrueType {};
+template<> struct IsPod<double>             : TrueType {};
+template<> struct IsPod<wchar_t>            : TrueType {};
+template<> struct IsPod<char16_t>           : TrueType {};
+template<typename T> struct IsPod<T*>       : TrueType {};
+
+namespace detail {
+
+// __is_empty is a supported extension across all of our supported compilers:
+// http://llvm.org/releases/3.0/docs/ClangReleaseNotes.html
+// http://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Type-Traits.html#Type-Traits
+// http://msdn.microsoft.com/en-us/library/ms177194%28v=vs.100%29.aspx
+template<typename T>
+struct IsEmptyHelper
+  : IntegralConstant<bool, IsClass<T>::value && __is_empty(T)>
+{};
+
+} // namespace detail
+
+/**
+ * IsEmpty determines whether a type is a class (but not a union) that is empty.
+ *
+ * A class is empty iff it and all its base classes have no non-static data
+ * members (except bit-fields of length 0) and no virtual member functions, and
+ * no base class is empty or a virtual base class.
+ *
+ * Intuitively, empty classes don't have any data that has to be stored in
+ * instances of those classes.  (The size of the class must still be non-zero,
+ * because distinct array elements of any type must have different addresses.
+ * However, if the Empty Base Optimization is implemented by the compiler [most
+ * compilers implement it, and in certain cases C++11 requires it], the size of
+ * a class inheriting from an empty |Base| class need not be inflated by
+ * |sizeof(Base)|.)  And intuitively, non-empty classes have data members and/or
+ * vtable pointers that must be stored in each instance for proper behavior.
+ *
+ *   static_assert(!mozilla::IsEmpty<int>::value, "not a class => not empty");
+ *   union U1 { int x; };
+ *   static_assert(!mozilla::IsEmpty<U1>::value, "not a class => not empty");
+ *   struct E1 {};
+ *   struct E2 { int : 0 };
+ *   struct E3 : E1 {};
+ *   struct E4 : E2 {};
+ *   static_assert(mozilla::IsEmpty<E1>::value &&
+ *                 mozilla::IsEmpty<E2>::value &&
+ *                 mozilla::IsEmpty<E3>::value &&
+ *                 mozilla::IsEmpty<E4>::value,
+ *                 "all empty");
+ *   union U2 { E1 e1; };
+ *   static_assert(!mozilla::IsEmpty<U2>::value, "not a class => not empty");
+ *   struct NE1 { int x; };
+ *   struct NE2 : virtual E1 {};
+ *   struct NE3 : E2 { virtual ~NE3() {} };
+ *   struct NE4 { virtual void f() {} };
+ *   static_assert(!mozilla::IsEmpty<NE1>::value &&
+ *                 !mozilla::IsEmpty<NE2>::value &&
+ *                 !mozilla::IsEmpty<NE3>::value &&
+ *                 !mozilla::IsEmpty<NE4>::value,
+ *                 "all empty");
+ */
+template<typename T>
+struct IsEmpty : detail::IsEmptyHelper<typename RemoveCV<T>::Type>
+{};
+
+
+namespace detail {
+
+template<typename T,
+         bool = IsFloatingPoint<T>::value,
+         bool = IsIntegral<T>::value,
+         typename NoCV = typename RemoveCV<T>::Type>
+struct IsSignedHelper;
+
+// Floating point is signed.
+template<typename T, typename NoCV>
+struct IsSignedHelper<T, true, false, NoCV> : TrueType {};
+
+// Integral is conditionally signed.
+template<typename T, typename NoCV>
+struct IsSignedHelper<T, false, true, NoCV>
+  : IntegralConstant<bool, bool(NoCV(-1) < NoCV(1))>
+{};
+
+// Non-floating point, non-integral is not signed.
+template<typename T, typename NoCV>
+struct IsSignedHelper<T, false, false, NoCV> : FalseType {};
+
+} // namespace detail
+
+/**
+ * IsSigned determines whether a type is a signed arithmetic type.  |char| is
+ * considered a signed type if it has the same representation as |signed char|.
+ *
+ * mozilla::IsSigned<int>::value is true;
+ * mozilla::IsSigned<const unsigned int>::value is false;
+ * mozilla::IsSigned<unsigned char>::value is false;
+ * mozilla::IsSigned<float>::value is true.
+ */
+template<typename T>
+struct IsSigned : detail::IsSignedHelper<T> {};
+
+namespace detail {
+
+template<typename T,
+         bool = IsFloatingPoint<T>::value,
+         bool = IsIntegral<T>::value,
+         typename NoCV = typename RemoveCV<T>::Type>
+struct IsUnsignedHelper;
+
+// Floating point is not unsigned.
+template<typename T, typename NoCV>
+struct IsUnsignedHelper<T, true, false, NoCV> : FalseType {};
+
+// Integral is conditionally unsigned.
+template<typename T, typename NoCV>
+struct IsUnsignedHelper<T, false, true, NoCV>
+  : IntegralConstant<bool,
+                     (IsSame<NoCV, bool>::value || bool(NoCV(1) < NoCV(-1)))>
+{};
+
+// Non-floating point, non-integral is not unsigned.
+template<typename T, typename NoCV>
+struct IsUnsignedHelper<T, false, false, NoCV> : FalseType {};
+
+} // namespace detail
+
+/**
+ * IsUnsigned determines whether a type is an unsigned arithmetic type.
+ *
+ * mozilla::IsUnsigned<int>::value is false;
+ * mozilla::IsUnsigned<const unsigned int>::value is true;
+ * mozilla::IsUnsigned<unsigned char>::value is true;
+ * mozilla::IsUnsigned<float>::value is false.
+ */
+template<typename T>
+struct IsUnsigned : detail::IsUnsignedHelper<T> {};
+
+namespace detail {
+
+struct DoIsDestructibleImpl
+{
+  template<typename T, typename = decltype(DeclVal<T&>().~T())>
+  static TrueType test(int);
+  template<typename T>
+  static FalseType test(...);
+};
+
+template<typename T>
+struct IsDestructibleImpl : public DoIsDestructibleImpl
+{
+  typedef decltype(test<T>(0)) Type;
+};
+
+} // namespace detail
+
+template<typename T>
+struct IsDestructible : public detail::IsDestructibleImpl<T>::Type {};
+
+/* 20.9.5 Type property queries [meta.unary.prop.query] */
+
+/* 20.9.6 Relationships between types [meta.rel] */
+
+/**
+ * IsSame tests whether two types are the same type.
+ *
+ * mozilla::IsSame<int, int>::value is true;
+ * mozilla::IsSame<int*, int*>::value is true;
+ * mozilla::IsSame<int, unsigned int>::value is false;
+ * mozilla::IsSame<void, void>::value is true;
+ * mozilla::IsSame<const int, int>::value is false;
+ * mozilla::IsSame<struct S, struct S>::value is true.
+ */
+template<typename T, typename U>
+struct IsSame : FalseType {};
+
+template<typename T>
+struct IsSame<T, T> : TrueType {};
+
+namespace detail {
+
+#if defined(__GNUC__) || defined(__clang__) || defined(_MSC_VER)
+
+template<class Base, class Derived>
+struct BaseOfTester : IntegralConstant<bool, __is_base_of(Base, Derived)> {};
+
+#else
+
+// The trickery used to implement IsBaseOf here makes it possible to use it for
+// the cases of private and multiple inheritance.  This code was inspired by the
+// sample code here:
+//
+// http://stackoverflow.com/questions/2910979/how-is-base-of-works
+template<class Base, class Derived>
+struct BaseOfHelper
+{
+public:
+  operator Base*() const;
+  operator Derived*();
+};
+
+template<class Base, class Derived>
+struct BaseOfTester
+{
+private:
+  template<class T>
+  static char test(Derived*, T);
+  static int test(Base*, int);
+
+public:
+  static const bool value =
+    sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char);
+};
+
+template<class Base, class Derived>
+struct BaseOfTester<Base, const Derived>
+{
+private:
+  template<class T>
+  static char test(Derived*, T);
+  static int test(Base*, int);
+
+public:
+  static const bool value =
+    sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char);
+};
+
+template<class Base, class Derived>
+struct BaseOfTester<Base&, Derived&> : FalseType {};
+
+template<class Type>
+struct BaseOfTester<Type, Type> : TrueType {};
+
+template<class Type>
+struct BaseOfTester<Type, const Type> : TrueType {};
+
+#endif
+
+} /* namespace detail */
+
+/*
+ * IsBaseOf allows to know whether a given class is derived from another.
+ *
+ * Consider the following class definitions:
+ *
+ *   class A {};
+ *   class B : public A {};
+ *   class C {};
+ *
+ * mozilla::IsBaseOf<A, B>::value is true;
+ * mozilla::IsBaseOf<A, C>::value is false;
+ */
+template<class Base, class Derived>
+struct IsBaseOf
+  : IntegralConstant<bool, detail::BaseOfTester<Base, Derived>::value>
+{};
+
+namespace detail {
+
+template<typename From, typename To>
+struct ConvertibleTester
+{
+private:
+  template<typename To1>
+  static char test_helper(To1);
+
+  template<typename From1, typename To1>
+  static decltype(test_helper<To1>(DeclVal<From1>())) test(int);
+
+  template<typename From1, typename To1>
+  static int test(...);
+
+public:
+  static const bool value =
+    sizeof(test<From, To>(0)) == sizeof(char);
+};
+
+} // namespace detail
+
+/**
+ * IsConvertible determines whether a value of type From will implicitly convert
+ * to a value of type To.  For example:
+ *
+ *   struct A {};
+ *   struct B : public A {};
+ *   struct C {};
+ *
+ * mozilla::IsConvertible<A, A>::value is true;
+ * mozilla::IsConvertible<A*, A*>::value is true;
+ * mozilla::IsConvertible<B, A>::value is true;
+ * mozilla::IsConvertible<B*, A*>::value is true;
+ * mozilla::IsConvertible<C, A>::value is false;
+ * mozilla::IsConvertible<A, C>::value is false;
+ * mozilla::IsConvertible<A*, C*>::value is false;
+ * mozilla::IsConvertible<C*, A*>::value is false.
+ *
+ * For obscure reasons, you can't use IsConvertible when the types being tested
+ * are related through private inheritance, and you'll get a compile error if
+ * you try.  Just don't do it!
+ *
+ * Note - we need special handling for void, which ConvertibleTester doesn't
+ * handle. The void handling here doesn't handle const/volatile void correctly,
+ * which could be easily fixed if the need arises.
+ */
+template<typename From, typename To>
+struct IsConvertible
+  : IntegralConstant<bool, detail::ConvertibleTester<From, To>::value>
+{};
+
+template<typename B>
+struct IsConvertible<void, B>
+  : IntegralConstant<bool, IsVoid<B>::value>
+{};
+
+template<typename A>
+struct IsConvertible<A, void>
+  : IntegralConstant<bool, IsVoid<A>::value>
+{};
+
+template<>
+struct IsConvertible<void, void>
+  : TrueType
+{};
+
+/* 20.9.7 Transformations between types [meta.trans] */
+
+/* 20.9.7.1 Const-volatile modifications [meta.trans.cv] */
+
+/**
+ * RemoveConst removes top-level const qualifications on a type.
+ *
+ * mozilla::RemoveConst<int>::Type is int;
+ * mozilla::RemoveConst<const int>::Type is int;
+ * mozilla::RemoveConst<const int*>::Type is const int*;
+ * mozilla::RemoveConst<int* const>::Type is int*.
+ */
+template<typename T>
+struct RemoveConst
+{
+  typedef T Type;
+};
+
+template<typename T>
+struct RemoveConst<const T>
+{
+  typedef T Type;
+};
+
+/**
+ * RemoveVolatile removes top-level volatile qualifications on a type.
+ *
+ * mozilla::RemoveVolatile<int>::Type is int;
+ * mozilla::RemoveVolatile<volatile int>::Type is int;
+ * mozilla::RemoveVolatile<volatile int*>::Type is volatile int*;
+ * mozilla::RemoveVolatile<int* volatile>::Type is int*.
+ */
+template<typename T>
+struct RemoveVolatile
+{
+  typedef T Type;
+};
+
+template<typename T>
+struct RemoveVolatile<volatile T>
+{
+  typedef T Type;
+};
+
+/**
+ * RemoveCV removes top-level const and volatile qualifications on a type.
+ *
+ * mozilla::RemoveCV<int>::Type is int;
+ * mozilla::RemoveCV<const int>::Type is int;
+ * mozilla::RemoveCV<volatile int>::Type is int;
+ * mozilla::RemoveCV<int* const volatile>::Type is int*.
+ */
+template<typename T>
+struct RemoveCV
+{
+  typedef typename RemoveConst<typename RemoveVolatile<T>::Type>::Type Type;
+};
+
+/* 20.9.7.2 Reference modifications [meta.trans.ref] */
+
+/**
+ * Converts reference types to the underlying types.
+ *
+ * mozilla::RemoveReference<T>::Type is T;
+ * mozilla::RemoveReference<T&>::Type is T;
+ * mozilla::RemoveReference<T&&>::Type is T;
+ */
+
+template<typename T>
+struct RemoveReference
+{
+  typedef T Type;
+};
+
+template<typename T>
+struct RemoveReference<T&>
+{
+  typedef T Type;
+};
+
+template<typename T>
+struct RemoveReference<T&&>
+{
+  typedef T Type;
+};
+
+template<bool Condition, typename A, typename B>
+struct Conditional;
+
+namespace detail {
+
+enum Voidness { TIsVoid, TIsNotVoid };
+
+template<typename T, Voidness V = IsVoid<T>::value ? TIsVoid : TIsNotVoid>
+struct AddLvalueReferenceHelper;
+
+template<typename T>
+struct AddLvalueReferenceHelper<T, TIsVoid>
+{
+  typedef void Type;
+};
+
+template<typename T>
+struct AddLvalueReferenceHelper<T, TIsNotVoid>
+{
+  typedef T& Type;
+};
+
+} // namespace detail
+
+/**
+ * AddLvalueReference adds an lvalue & reference to T if one isn't already
+ * present. (Note: adding an lvalue reference to an rvalue && reference in
+ * essence replaces the && with a &&, per C+11 reference collapsing rules. For
+ * example, int&& would become int&.)
+ *
+ * The final computed type will only *not* be an lvalue reference if T is void.
+ *
+ * mozilla::AddLvalueReference<int>::Type is int&;
+ * mozilla::AddLvalueRference<volatile int&>::Type is volatile int&;
+ * mozilla::AddLvalueReference<void*>::Type is void*&;
+ * mozilla::AddLvalueReference<void>::Type is void;
+ * mozilla::AddLvalueReference<struct S&&>::Type is struct S&.
+ */
+template<typename T>
+struct AddLvalueReference
+  : detail::AddLvalueReferenceHelper<T>
+{};
+
+namespace detail {
+
+template<typename T, Voidness V = IsVoid<T>::value ? TIsVoid : TIsNotVoid>
+struct AddRvalueReferenceHelper;
+
+template<typename T>
+struct AddRvalueReferenceHelper<T, TIsVoid>
+{
+  typedef void Type;
+};
+
+template<typename T>
+struct AddRvalueReferenceHelper<T, TIsNotVoid>
+{
+  typedef T&& Type;
+};
+
+} // namespace detail
+
+/**
+ * AddRvalueReference adds an rvalue && reference to T if one isn't already
+ * present. (Note: adding an rvalue reference to an lvalue & reference in
+ * essence keeps the &, per C+11 reference collapsing rules. For example,
+ * int& would remain int&.)
+ *
+ * The final computed type will only *not* be a reference if T is void.
+ *
+ * mozilla::AddRvalueReference<int>::Type is int&&;
+ * mozilla::AddRvalueRference<volatile int&>::Type is volatile int&;
+ * mozilla::AddRvalueRference<const int&&>::Type is const int&&;
+ * mozilla::AddRvalueReference<void*>::Type is void*&&;
+ * mozilla::AddRvalueReference<void>::Type is void;
+ * mozilla::AddRvalueReference<struct S&>::Type is struct S&.
+ */
+template<typename T>
+struct AddRvalueReference
+  : detail::AddRvalueReferenceHelper<T>
+{};
+
+/* 20.9.7.3 Sign modifications [meta.trans.sign] */
+
+template<bool B, typename T = void>
+struct EnableIf;
+
+namespace detail {
+
+template<bool MakeConst, typename T>
+struct WithC : Conditional<MakeConst, const T, T>
+{};
+
+template<bool MakeVolatile, typename T>
+struct WithV : Conditional<MakeVolatile, volatile T, T>
+{};
+
+
+template<bool MakeConst, bool MakeVolatile, typename T>
+struct WithCV : WithC<MakeConst, typename WithV<MakeVolatile, T>::Type>
+{};
+
+template<typename T>
+struct CorrespondingSigned;
+
+template<>
+struct CorrespondingSigned<char> { typedef signed char Type; };
+template<>
+struct CorrespondingSigned<unsigned char> { typedef signed char Type; };
+template<>
+struct CorrespondingSigned<unsigned short> { typedef short Type; };
+template<>
+struct CorrespondingSigned<unsigned int> { typedef int Type; };
+template<>
+struct CorrespondingSigned<unsigned long> { typedef long Type; };
+template<>
+struct CorrespondingSigned<unsigned long long> { typedef long long Type; };
+
+template<typename T,
+         typename CVRemoved = typename RemoveCV<T>::Type,
+         bool IsSignedIntegerType = IsSigned<CVRemoved>::value &&
+                                    !IsSame<char, CVRemoved>::value>
+struct MakeSigned;
+
+template<typename T, typename CVRemoved>
+struct MakeSigned<T, CVRemoved, true>
+{
+  typedef T Type;
+};
+
+template<typename T, typename CVRemoved>
+struct MakeSigned<T, CVRemoved, false>
+  : WithCV<IsConst<T>::value, IsVolatile<T>::value,
+           typename CorrespondingSigned<CVRemoved>::Type>
+{};
+
+} // namespace detail
+
+/**
+ * MakeSigned produces the corresponding signed integer type for a given
+ * integral type T, with the const/volatile qualifiers of T.  T must be a
+ * possibly-const/volatile-qualified integral type that isn't bool.
+ *
+ * If T is already a signed integer type (not including char!), then T is
+ * produced.
+ *
+ * Otherwise, if T is an unsigned integer type, the signed variety of T, with
+ * T's const/volatile qualifiers, is produced.
+ *
+ * Otherwise, the integral type of the same size as T, with the lowest rank,
+ * with T's const/volatile qualifiers, is produced.  (This basically only acts
+ * to produce signed char when T = char.)
+ *
+ * mozilla::MakeSigned<unsigned long>::Type is signed long;
+ * mozilla::MakeSigned<volatile int>::Type is volatile int;
+ * mozilla::MakeSigned<const unsigned short>::Type is const signed short;
+ * mozilla::MakeSigned<const char>::Type is const signed char;
+ * mozilla::MakeSigned<bool> is an error;
+ * mozilla::MakeSigned<void*> is an error.
+ */
+template<typename T>
+struct MakeSigned
+  : EnableIf<IsIntegral<T>::value &&
+             !IsSame<bool, typename RemoveCV<T>::Type>::value,
+             typename detail::MakeSigned<T>
+            >::Type
+{};
+
+namespace detail {
+
+template<typename T>
+struct CorrespondingUnsigned;
+
+template<>
+struct CorrespondingUnsigned<char> { typedef unsigned char Type; };
+template<>
+struct CorrespondingUnsigned<signed char> { typedef unsigned char Type; };
+template<>
+struct CorrespondingUnsigned<short> { typedef unsigned short Type; };
+template<>
+struct CorrespondingUnsigned<int> { typedef unsigned int Type; };
+template<>
+struct CorrespondingUnsigned<long> { typedef unsigned long Type; };
+template<>
+struct CorrespondingUnsigned<long long> { typedef unsigned long long Type; };
+
+
+template<typename T,
+         typename CVRemoved = typename RemoveCV<T>::Type,
+         bool IsUnsignedIntegerType = IsUnsigned<CVRemoved>::value &&
+                                      !IsSame<char, CVRemoved>::value>
+struct MakeUnsigned;
+
+template<typename T, typename CVRemoved>
+struct MakeUnsigned<T, CVRemoved, true>
+{
+  typedef T Type;
+};
+
+template<typename T, typename CVRemoved>
+struct MakeUnsigned<T, CVRemoved, false>
+  : WithCV<IsConst<T>::value, IsVolatile<T>::value,
+           typename CorrespondingUnsigned<CVRemoved>::Type>
+{};
+
+} // namespace detail
+
+/**
+ * MakeUnsigned produces the corresponding unsigned integer type for a given
+ * integral type T, with the const/volatile qualifiers of T.  T must be a
+ * possibly-const/volatile-qualified integral type that isn't bool.
+ *
+ * If T is already an unsigned integer type (not including char!), then T is
+ * produced.
+ *
+ * Otherwise, if T is an signed integer type, the unsigned variety of T, with
+ * T's const/volatile qualifiers, is produced.
+ *
+ * Otherwise, the unsigned integral type of the same size as T, with the lowest
+ * rank, with T's const/volatile qualifiers, is produced.  (This basically only
+ * acts to produce unsigned char when T = char.)
+ *
+ * mozilla::MakeUnsigned<signed long>::Type is unsigned long;
+ * mozilla::MakeUnsigned<volatile unsigned int>::Type is volatile unsigned int;
+ * mozilla::MakeUnsigned<const signed short>::Type is const unsigned short;
+ * mozilla::MakeUnsigned<const char>::Type is const unsigned char;
+ * mozilla::MakeUnsigned<bool> is an error;
+ * mozilla::MakeUnsigned<void*> is an error.
+ */
+template<typename T>
+struct MakeUnsigned
+  : EnableIf<IsIntegral<T>::value &&
+             !IsSame<bool, typename RemoveCV<T>::Type>::value,
+             typename detail::MakeUnsigned<T>
+            >::Type
+{};
+
+/* 20.9.7.4 Array modifications [meta.trans.arr] */
+
+/**
+ * RemoveExtent produces either the type of the elements of the array T, or T
+ * itself.
+ *
+ * mozilla::RemoveExtent<int>::Type is int;
+ * mozilla::RemoveExtent<const int[]>::Type is const int;
+ * mozilla::RemoveExtent<volatile int[5]>::Type is volatile int;
+ * mozilla::RemoveExtent<long[][17]>::Type is long[17].
+ */
+template<typename T>
+struct RemoveExtent
+{
+  typedef T Type;
+};
+
+template<typename T>
+struct RemoveExtent<T[]>
+{
+  typedef T Type;
+};
+
+template<typename T, decltype(sizeof(1)) N>
+struct RemoveExtent<T[N]>
+{
+  typedef T Type;
+};
+
+/* 20.9.7.5 Pointer modifications [meta.trans.ptr] */
+
+namespace detail {
+
+template<typename T, typename CVRemoved>
+struct RemovePointerHelper
+{
+  typedef T Type;
+};
+
+template<typename T, typename Pointee>
+struct RemovePointerHelper<T, Pointee*>
+{
+  typedef Pointee Type;
+};
+
+} // namespace detail
+
+/**
+ * Produces the pointed-to type if a pointer is provided, else returns the input
+ * type.  Note that this does not dereference pointer-to-member pointers.
+ *
+ * struct S { bool m; void f(); };
+ * mozilla::RemovePointer<int>::Type is int;
+ * mozilla::RemovePointer<int*>::Type is int;
+ * mozilla::RemovePointer<int* const>::Type is int;
+ * mozilla::RemovePointer<int* volatile>::Type is int;
+ * mozilla::RemovePointer<const long*>::Type is const long;
+ * mozilla::RemovePointer<void* const>::Type is void;
+ * mozilla::RemovePointer<void (S::*)()>::Type is void (S::*)();
+ * mozilla::RemovePointer<void (*)()>::Type is void();
+ * mozilla::RemovePointer<bool S::*>::Type is bool S::*.
+ */
+template<typename T>
+struct RemovePointer
+  : detail::RemovePointerHelper<T, typename RemoveCV<T>::Type>
+{};
+
+/**
+ * Converts T& to T*. Otherwise returns T* given T. Note that C++17 wants
+ * std::add_pointer to work differently for function types. We don't implement
+ * that behavior here.
+ *
+ * mozilla::AddPointer<int> is int*;
+ * mozilla::AddPointer<int*> is int**;
+ * mozilla::AddPointer<int&> is int*;
+ * mozilla::AddPointer<int* const> is int** const.
+ */
+template<typename T>
+struct AddPointer
+{
+  typedef typename RemoveReference<T>::Type* Type;
+};
+
+/* 20.9.7.6 Other transformations [meta.trans.other] */
+
+/**
+ * EnableIf is a struct containing a typedef of T if and only if B is true.
+ *
+ * mozilla::EnableIf<true, int>::Type is int;
+ * mozilla::EnableIf<false, int>::Type is a compile-time error.
+ *
+ * Use this template to implement SFINAE-style (Substitution Failure Is not An
+ * Error) requirements.  For example, you might use it to impose a restriction
+ * on a template parameter:
+ *
+ *   template<typename T>
+ *   class PodVector // vector optimized to store POD (memcpy-able) types
+ *   {
+ *      EnableIf<IsPod<T>::value, T>::Type* vector;
+ *      size_t length;
+ *      ...
+ *   };
+ */
+template<bool B, typename T>
+struct EnableIf
+{};
+
+template<typename T>
+struct EnableIf<true, T>
+{
+  typedef T Type;
+};
+
+/**
+ * Conditional selects a class between two, depending on a given boolean value.
+ *
+ * mozilla::Conditional<true, A, B>::Type is A;
+ * mozilla::Conditional<false, A, B>::Type is B;
+ */
+template<bool Condition, typename A, typename B>
+struct Conditional
+{
+  typedef A Type;
+};
+
+template<class A, class B>
+struct Conditional<false, A, B>
+{
+  typedef B Type;
+};
+
+namespace detail {
+
+template<typename U,
+         bool IsArray = IsArray<U>::value,
+         bool IsFunction = IsFunction<U>::value>
+struct DecaySelector;
+
+template<typename U>
+struct DecaySelector<U, false, false>
+{
+  typedef typename RemoveCV<U>::Type Type;
+};
+
+template<typename U>
+struct DecaySelector<U, true, false>
+{
+  typedef typename RemoveExtent<U>::Type* Type;
+};
+
+template<typename U>
+struct DecaySelector<U, false, true>
+{
+  typedef typename AddPointer<U>::Type Type;
+};
+
+}; // namespace detail
+
+/**
+ * Strips const/volatile off a type and decays it from an lvalue to an
+ * rvalue. So function types are converted to function pointers, arrays to
+ * pointers, and references are removed.
+ *
+ * mozilla::Decay<int>::Type is int
+ * mozilla::Decay<int&>::Type is int
+ * mozilla::Decay<int&&>::Type is int
+ * mozilla::Decay<const int&>::Type is int
+ * mozilla::Decay<int[2]>::Type is int*
+ * mozilla::Decay<int(int)>::Type is int(*)(int)
+ */
+template<typename T>
+class Decay
+  : public detail::DecaySelector<typename RemoveReference<T>::Type>
+{
+};
+
+} /* namespace mozilla */
+
+#endif /* mozilla_TypeTraits_h */
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