hybrid_adapter: fix infinite recursion error with Clang

Author: Morwenn

include/cpp-sort/adapters/hybrid_adapter.h

@@ -213,13 +213,13 @@ namespace cppsort
 
                 template<typename Self, mstd::forward_range Range, typename... Args>
                 constexpr auto operator()(this Self&& self, Range&& range, Args&&... args)
-                    -> decltype(std::forward<Self>(self).base_class::operator()(
+                    -> decltype(static_cast<detail::copy_cvref_t<Self, base_class>>(self)(
                         detail::choice_for_it<mstd::iterator_t<Range>, sizeof...(Sorters)>{},
                         std::forward<Range>(range),
                         std::forward<Args>(args)...
                     ))
                 {
-                    return std::forward<Self>(self).base_class::operator()(
+                    return static_cast<detail::copy_cvref_t<Self, base_class>>(self)(
                         detail::choice_for_it<mstd::iterator_t<Range>, sizeof...(Sorters)>{},
                         std::forward<Range>(range),
                         std::forward<Args>(args)...
@@ -233,13 +233,13 @@ namespace cppsort
                     typename... Args
                 >
                 constexpr auto operator()(this Self&& self, Iterator first, Sentinel last, Args&&... args)
-                    -> decltype(std::forward<Self>(self).base_class::operator()(
+                    -> decltype(static_cast<detail::copy_cvref_t<Self, base_class>>(self)(
                             detail::choice_for_it<Iterator, sizeof...(Sorters)>{},
                             std::move(first), std::move(last),
                             std::forward<Args>(args)...
                     ))
                 {
-                    return std::forward<Self>(self).base_class::operator()(
+                    return static_cast<detail::copy_cvref_t<Self, base_class>>(self)(
                         detail::choice_for_it<Iterator, sizeof...(Sorters)>{},
                         std::move(first), std::move(last),
                         std::forward<Args>(args)...