[libcxx-commits] [PATCH] D145376: [libc++] add declval failure assertion for instantiation

[Igor Zhukov via Phabricator via libcxx-commits]

fsb4000 added inline comments.


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Comment at: libcxx/include/__utility/declval.h:29
 
-template <class _Tp>
-decltype(std::__declval<_Tp>(0)) declval() _NOEXCEPT;
+template <class _Tp, bool _False = false>
+_LIBCPP_HIDE_FROM_ABI decltype(std::__declval<_Tp>(0)) declval() _NOEXCEPT {
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frederick-vs-ja wrote:
> I think it's better not to modify the template head.
> Doesn't libc++ have a concentrated `__dependent_false`? If so, I think we can still use `!__is_same(_Tp, _Tp)` in `static_assert`.
I found that pattern there: https://github.com/llvm/llvm-project/blob/90f6a4cc73d5c40add913e6ed5d34a7a9db58c79/libcxx/include/__compare/common_comparison_category.h#L63-L79


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https://reviews.llvm.org/D145376