Now that these internal type traits are again class templates, it's better to derive from the trait's ::type (which is either false_type or true_type) instead of from the trait itself, for sake of a shallower inheritance chain. We usually do this but not always; this patch makes us consistently do so.
Tested on x86_64-pc-lnux-gnu, does this look OK for trunk? (Compile time for join.cc decreases by about 0.5% with this, avg of 10 runs.) libstdc++-v3/ChangeLog: * include/std/tuple (tuple::_UseOtherCtor): Do ::type when deriving from __and_, __or_ or __not_. * include/std/type_traits (negation): Likewise. (is_unsigned): Likewise. (__is_implicitly_default_constructible): Likewise. (is_trivially_destructible): Likewise. (__is_nt_invocable_impl): Likewise. --- libstdc++-v3/include/std/tuple | 2 +- libstdc++-v3/include/std/type_traits | 10 +++++----- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple index ddd7c226d80..26e248431ec 100644 --- a/libstdc++-v3/include/std/tuple +++ b/libstdc++-v3/include/std/tuple @@ -826,7 +826,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // then TUPLE should match tuple(UTypes&&...) instead. template<typename _Tuple, typename _Tp, typename _Up> struct _UseOtherCtor<_Tuple, tuple<_Tp>, tuple<_Up>> - : __or_<is_convertible<_Tuple, _Tp>, is_constructible<_Tp, _Tuple>> + : __or_<is_convertible<_Tuple, _Tp>, is_constructible<_Tp, _Tuple>>::type { }; // If TUPLE and *this each have a single element of the same type, // then TUPLE should match a copy/move constructor instead. diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index be9f2955539..c0bb1cf64e3 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -235,7 +235,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Pp> struct negation - : __not_<_Pp> + : __not_<_Pp>::type { }; /** @ingroup variable_templates @@ -845,7 +845,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// is_unsigned template<typename _Tp> struct is_unsigned - : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>> + : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>::type { }; /// @cond undocumented @@ -1222,7 +1222,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template <typename _Tp> struct __is_implicitly_default_constructible : public __and_<__is_constructible_impl<_Tp>, - __is_implicitly_default_constructible_safe<_Tp>> + __is_implicitly_default_constructible_safe<_Tp>>::type { }; /// is_trivially_copy_constructible @@ -1282,7 +1282,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Tp> struct is_trivially_destructible : public __and_<__is_destructible_safe<_Tp>, - __bool_constant<__has_trivial_destructor(_Tp)>> + __bool_constant<__has_trivial_destructor(_Tp)>>::type { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -2975,7 +2975,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct __is_nt_invocable_impl<_Result, _Ret, __void_t<typename _Result::type>> : __or_<is_void<_Ret>, - __is_nothrow_convertible<typename _Result::type, _Ret>> + __is_nothrow_convertible<typename _Result::type, _Ret>>::type { }; /// @endcond -- 2.37.2.490.g6c8e4ee870