Pull in r233552 from upstream libc++ trunk (by Eric Fiselier):
[libcxx] Fix PR22771 - Support access control SFINAE in the library version of is_convertible. Summary: Currently the conversion check does not take place in a context where access control SFINAE is applied. This patch changes the context of the test expression so that SFINAE occurs if access control does not permit the conversion. Related bug: https://llvm.org/bugs/show_bug.cgi?id=22771 Reviewers: mclow.lists, rsmith, dim Reviewed By: dim Subscribers: dim, rodrigc, emaste, cfe-commits Differential Revision: http://reviews.llvm.org/D8461 This fixes building clang, and other programs using libc++, with newer versions of gcc (specifically, gcc 4.8 and higher). Reported by: rodrigc MFC after: 1 week
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@ -842,7 +842,16 @@ template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY is_convertible
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namespace __is_convertible_imp
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{
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template <class _Tp> char __test(_Tp);
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template <class _Tp> void __test_convert(_Tp);
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template <class _From, class _To, class = void>
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struct __is_convertible_test : public false_type {};
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template <class _From, class _To>
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struct __is_convertible_test<_From, _To,
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decltype(__test_convert<_To>(_VSTD::declval<_From>()))> : public true_type
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{};
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template <class _Tp> __two __test(...);
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#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
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template <class _Tp> _Tp&& __source();
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@ -877,10 +886,8 @@ template <class _T1, class _T2,
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unsigned _T2_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T2>::value>
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struct __is_convertible
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: public integral_constant<bool,
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#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
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sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
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#else
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sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
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__is_convertible_imp::__is_convertible_test<_T1, _T2>::value
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#if defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
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&& !(!is_function<_T1>::value && !is_reference<_T1>::value && is_reference<_T2>::value
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&& (!is_const<typename remove_reference<_T2>::type>::value
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|| is_volatile<typename remove_reference<_T2>::type>::value)
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