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 90e86b7c61bfb541fc25b7097f9d7d2a41f49cb9..a31b7e772388a5dc0a4e470c0f5aca1383c38c4c 100644 (file)
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1151,7 +1151,6 @@ 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);
     }
@@ -1162,7 +1161,6 @@ 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));
     }
@@ -1173,7 +1171,6 @@ 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);
     }
@@ -1184,7 +1181,6 @@ 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));
     }