libstdc++: Remove non-void static assertions in variant's std::get [PR111172]

A void template argument would cause a substitution failure when trying
to form a reference for the return type, so the function body would
never be instantiated.

libstdc++-v3/ChangeLog:

	PR libstdc++/111172
	* include/std/variant (get<T>): Remove !is_void static
	assertions.

(cherry picked from commit d19bdf8874059457fdfe50a9e14dad8f8b8cecbb)

diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 64145da12bb3a23f47bac7fbea861e29757c1ab1..9abe7b9ed6d755fc1e6b43c8ae527d2244364140 100644 (file)
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1150,7 +1150,6 @@ namespace __variant
     {
       static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
                    "T must occur exactly once in alternatives");
-      static_assert(!is_void_v<_Tp>, "_Tp must not be void");
       constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>();
       return std::get<__n>(__v);
     }
@@ -1161,7 +1160,6 @@ namespace __variant
     {
       static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
                    "T must occur exactly once in alternatives");
-      static_assert(!is_void_v<_Tp>, "_Tp must not be void");
       constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>();
       return std::get<__n>(std::move(__v));
     }
@@ -1172,7 +1170,6 @@ namespace __variant
     {
       static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
                    "T must occur exactly once in alternatives");
-      static_assert(!is_void_v<_Tp>, "_Tp must not be void");
       constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>();
       return std::get<__n>(__v);
     }
@@ -1183,7 +1180,6 @@ namespace __variant
     {
       static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
                    "T must occur exactly once in alternatives");
-      static_assert(!is_void_v<_Tp>, "_Tp must not be void");
       constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>();
       return std::get<__n>(std::move(__v));
     }