EricWF added inline comments.
================
Comment at: include/variant:1109
+#define _LIBCPP_VARIANT_BOOLEAN_CONVERSION(bool_type) \
+ template <class... _Types> \
----------------
EricWF wrote:
> I would like to see a version of this patch that doesn't use preprocessor
> expansion to specialize `__overload` multiple times.
>
> Perhaps adding a `bool = is_same<remove_cv_t<First>, bool>` to `__overload`
> and then specializing once on that?
Or perhaps SFINAE-ing the `test` member instead of specializing `__overload`.
Something like this maybe?
```
template <class _Tp, class... _Types>
struct __overload< _Tp, _Types...> : __overload<_Types...>
{
using __overload<_Types...>::operator();
template <bool _EnableBool>
using _DepIsBool = typename __dependent_type<
enable_if<is_same_v<remove_cv_t<_Tp>, bool> == _EnableBool>, _EnableBool
>::type;
template <class _Up, bool _EnableBool = false, class =
_DepIsBool<_EnableBool>>
auto operator()(_Tp, _Up&& __t) const
-> decltype(_Tp{__t}, __identity<_Tp>());
template <class _Up, class _Ap = __uncvref_t<_Up>,
bool _EnableIfBool = true, class = _DepIsBool<_EnableIfBool>>
auto operator()(bool, _Up&&, int _Ap::*) const
-> __identity<_Tp>;
template <class _Up, class _Ap = __uncvref_t<_Up>,
bool _EnableIfBool = true, class = _DepIsBool<_EnableIfBool>>
auto operator()(bool, _Up&&) const
-> enable_if_t<is_same_v<_Ap, bool>, __identity<_Tp>>;
};
```
Repository:
rCXX libc++
https://reviews.llvm.org/D44865
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