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TypeTraits.h
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/* -*- 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 constexpr 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 DoIsDefaultConstructibleImpl
{
template<typename T, typename = decltype(T())>
static TrueType test(int);
template<typename T>
static FalseType test(...);
};
template<typename T>
struct IsDefaultConstructibleImpl : public DoIsDefaultConstructibleImpl
{
typedef decltype(test<T>(0)) Type;
};
} // namespace detail
/**
* IsDefaultConstructible determines whether a type has a public default
* constructor.
*
* struct S0 {}; // Implicit default constructor.
* struct S1 { S1(); };
* struct S2 { explicit S2(int); }; // No implicit default constructor when
* // another one is present.
* struct S3 { S3() = delete; };
* class C4 { C4(); }; // Default constructor is private.
*
* mozilla::IsDefaultConstructible<int>::value is true;
* mozilla::IsDefaultConstructible<S0>::value is true;
* mozilla::IsDefaultConstructible<S1>::value is true;
* mozilla::IsDefaultConstructible<S2>::value is false;
* mozilla::IsDefaultConstructible<S3>::value is false;
* mozilla::IsDefaultConstructible<S4>::value is false.
*/
template<typename T>
struct IsDefaultConstructible
: public detail::IsDefaultConstructibleImpl<T>::Type
{};
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
/**
* IsDestructible determines whether a type has a public destructor.
*
* struct S0 {}; // Implicit default destructor.
* struct S1 { ~S1(); };
* class C2 { ~C2(); }; // private destructor.
*
* mozilla::IsDestructible<S0>::value is true;
* mozilla::IsDestructible<S1>::value is true;
* mozilla::IsDestructible<C2>::value is false.
*/
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>
{};