This defines the equivalent of C++2a's std::type_identity_t alias but
for use in C++11 and later. This can be used to replace __detail::__idt
in the string_view headers, which previously used common_type_t because
the one argument specialization of common_type_t was simply the identity
transform (which is no longer true).
* include/experimental/string_view (__detail::__idt): Remove.
(operator==, operator!=, operator<, operator>, operator<=, operator>=):
Use __type_identity_t instead of __detail::__idt;
* include/std/string_view (__detail::__idt): Remove.
(operator==, operator!=, operator<, operator>, operator<=, operator>=):
Use __type_identity_t instead of __detail::__idt;
* include/std/type_traits (__type_identity_t): New alias template.
Tested x86_64-linux, committed to trunk.
commit 1cb3c8671d1bfb7b4dff2a707deaf113c071e442
Author: redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri Jul 12 11:43:22 2019 +0000
Define __type_identity_t alias and use for string_view
This defines the equivalent of C++2a's std::type_identity_t alias but
for use in C++11 and later. This can be used to replace __detail::__idt
in the string_view headers, which previously used common_type_t because
the one argument specialization of common_type_t was simply the identity
transform (which is no longer true).
* include/experimental/string_view (__detail::__idt): Remove.
(operator==, operator!=, operator<, operator>, operator<=,
operator>=):
Use __type_identity_t instead of __detail::__idt;
* include/std/string_view (__detail::__idt): Remove.
(operator==, operator!=, operator<, operator>, operator<=,
operator>=):
Use __type_identity_t instead of __detail::__idt;
* include/std/type_traits (__type_identity_t): New alias template.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@273442
138bc75d-0d04-0410-961f-82ee72b054a4
diff --git a/libstdc++-v3/include/experimental/string_view
b/libstdc++-v3/include/experimental/string_view
index 9449869367c..84b2a3eb402 100644
--- a/libstdc++-v3/include/experimental/string_view
+++ b/libstdc++-v3/include/experimental/string_view
@@ -436,14 +436,10 @@ inline namespace fundamentals_v1
// [string.view.comparison], non-member basic_string_view comparison
functions
- namespace __detail
- {
- // Identity transform to create a non-deduced context, so that only one
- // argument participates in template argument deduction and the other
- // argument gets implicitly converted to the deduced type. See n3766.html.
- template<typename _Tp>
- using __idt = common_type_t<_Tp>;
- }
+ // Several of these functions use type_identity_t to create a non-deduced
+ // context, so that only one argument participates in template argument
+ // deduction and the other argument gets implicitly converted to the deduced
+ // type (see N3766).
template<typename _CharT, typename _Traits>
constexpr bool
@@ -454,12 +450,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator==(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.size() == __y.size() && __x.compare(__y) == 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.size() == __y.size() && __x.compare(__y) == 0; }
@@ -472,12 +469,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator!=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return !(__x == __y); }
template<typename _CharT, typename _Traits>
constexpr bool
- operator!=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return !(__x == __y); }
@@ -490,12 +488,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator< (basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) < 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator< (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) < 0; }
@@ -508,12 +507,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator> (basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) > 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator> (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) > 0; }
@@ -526,12 +526,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator<=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) <= 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator<=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) <= 0; }
@@ -544,12 +545,13 @@ inline namespace fundamentals_v1
template<typename _CharT, typename _Traits>
constexpr bool
operator>=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) >= 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator>=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) >= 0; }
diff --git a/libstdc++-v3/include/std/string_view
b/libstdc++-v3/include/std/string_view
index 42822cc41ab..e8b6ed3af12 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -459,14 +459,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// [string.view.comparison], non-member basic_string_view comparison function
- namespace __detail
- {
- // Identity transform to create a non-deduced context, so that only one
- // argument participates in template argument deduction and the other
- // argument gets implicitly converted to the deduced type. See n3766.html.
- template<typename _Tp>
- using __idt = common_type_t<_Tp>;
- }
+ // Several of these functions use type_identity_t to create a non-deduced
+ // context, so that only one argument participates in template argument
+ // deduction and the other argument gets implicitly converted to the deduced
+ // type (see N3766).
template<typename _CharT, typename _Traits>
constexpr bool
@@ -477,12 +473,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator==(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.size() == __y.size() && __x.compare(__y) == 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.size() == __y.size() && __x.compare(__y) == 0; }
@@ -495,12 +492,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator!=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return !(__x == __y); }
template<typename _CharT, typename _Traits>
constexpr bool
- operator!=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return !(__x == __y); }
@@ -513,12 +511,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator< (basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) < 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator< (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) < 0; }
@@ -531,12 +530,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator> (basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) > 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator> (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) > 0; }
@@ -549,12 +549,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator<=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) <= 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator<=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) <= 0; }
@@ -567,12 +568,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT, typename _Traits>
constexpr bool
operator>=(basic_string_view<_CharT, _Traits> __x,
- __detail::__idt<basic_string_view<_CharT, _Traits>> __y)
noexcept
+ __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
+ noexcept
{ return __x.compare(__y) >= 0; }
template<typename _CharT, typename _Traits>
constexpr bool
- operator>=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+ operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
basic_string_view<_CharT, _Traits> __y) noexcept
{ return __x.compare(__y) >= 0; }
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index b07291706ac..d8ed1ce120d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -92,9 +92,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct conditional;
template <typename _Type>
- struct __type_identity {
- using type = _Type;
- };
+ struct __type_identity
+ { using type = _Type; };
+
+ template<typename _Tp>
+ using __type_identity_t = typename __type_identity<_Tp>::type;
template<typename...>
struct __or_;
