libstdc++: Make variant_npos conversions explicit [PR 96766]

libstdc++-v3/ChangeLog:

	PR libstdc++/96766
	* include/std/variant (_Variant_storage): Replace implicit
	conversions from size_t to __index_type with explicit casts.

(cherry picked from commit 074436cf8cdd2a9ce75cadd36deb8301f00e55b9)

diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index e1882b367004fd19df6ca122c4cba712fdb8d3e6..91fec0baab6b0a4257cecde3676b2370f7c691a2 100644 (file)
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -372,12 +372,16 @@ namespace __variant
   template<typename... _Types>
     struct _Variant_storage<false, _Types...>
     {
-      constexpr _Variant_storage() : _M_index(variant_npos) { }
+      constexpr
+      _Variant_storage()
+      : _M_index(static_cast<__index_type>(variant_npos))
+      { }
 
       template<size_t _Np, typename... _Args>
-       constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
+       constexpr
+       _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
        : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
-       _M_index(_Np)
+       _M_index{_Np}
        { }
 
       constexpr void _M_reset_impl()
@@ -395,7 +399,7 @@ namespace __variant
       void _M_reset()
       {
        _M_reset_impl();
-       _M_index = variant_npos;
+       _M_index = static_cast<__index_type>(variant_npos);
       }
 
       ~_Variant_storage()
@@ -424,16 +428,20 @@ namespace __variant
   template<typename... _Types>
     struct _Variant_storage<true, _Types...>
     {
-      constexpr _Variant_storage() : _M_index(variant_npos) { }
+      constexpr
+      _Variant_storage()
+      : _M_index(static_cast<__index_type>(variant_npos))
+      { }
 
       template<size_t _Np, typename... _Args>
-       constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
+       constexpr
+       _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
        : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
-       _M_index(_Np)
+       _M_index{_Np}
        { }
 
       void _M_reset()
-      { _M_index = variant_npos; }
+      { _M_index = static_cast<__index_type>(variant_npos); }
 
       void*
       _M_storage() const
@@ -447,7 +455,7 @@ namespace __variant
       {
        if constexpr (__never_valueless<_Types...>())
          return true;
-       return this->_M_index != __index_type(variant_npos);
+       return this->_M_index != static_cast<__index_type>(variant_npos);
       }
 
       _Variadic_union<_Types...> _M_u;