replace custom scope guard with generic one in __any

Author: ericniebler

include/stdexec/__detail/__any.hpp

@@ -26,6 +26,7 @@ import stdexec;
 #  include "__concepts.hpp"
 #  include "__config.hpp"
 #  include "__memory.hpp"
+#  include "__scope.hpp"
 #  include "__type_traits.hpp"
 #  include "__typeinfo.hpp"
 #  include "__utility.hpp"
@@ -37,6 +38,7 @@ import stdexec;
 
 #    include <bit>
 #    include <exception>
+#    include <functional>
 #    include <memory>
 #    include <span>
 #    include <type_traits>
@@ -614,27 +616,6 @@ namespace STDEXEC::__any
 
   //////////////////////////////////////////////////////////////////////////////////////////
   // __emplace_into
-  template <class _Alloc2>
-  struct __dealloc_guard
-  {
-    _Alloc2                                         &__alloc;
-    typename std::allocator_traits<_Alloc2>::pointer __ptr;
-    bool                                             __dismissed = false;
-
-    constexpr void __dismiss() noexcept
-    {
-      __dismissed = true;
-    }
-
-    constexpr ~__dealloc_guard() noexcept
-    {
-      if (!__dismissed)
-      {
-        std::allocator_traits<_Alloc2>::deallocate(__alloc, __ptr, 1);
-      }
-    }
-  };
-
   template <class _Model, class _Allocator, class... _Args>
   constexpr _Model &__emplace_into([[maybe_unused]] _Allocator const    &__alloc,
                                    [[maybe_unused]] __iroot            *&__root_ptr,
@@ -656,12 +637,14 @@ namespace STDEXEC::__any
       }
       else
       {
-        auto __alloc2                               = STDEXEC::__rebind_allocator<_Model>(__alloc);
-        using __traits_t                            = std::allocator_traits<decltype(__alloc2)>;
-        auto *const                         __model = __traits_t::allocate(__alloc2, 1);
-        __dealloc_guard<decltype(__alloc2)> __guard{__alloc2, __model};
+        auto __alloc2       = STDEXEC::__rebind_allocator<_Model>(__alloc);
+        using __traits_t    = std::allocator_traits<decltype(__alloc2)>;
+        auto *const __model = __traits_t::allocate(__alloc2, 1);
+
+        auto __guard = __scope_guard{&__traits_t::deallocate, std::ref(__alloc2), __model, 1};
         __traits_t::construct(__alloc2, __model, static_cast<_Args &&>(__args)...);
         __guard.__dismiss();
+
         *__std::start_lifetime_as<__tagged_ptr>(__buff.data()) = __tagged_ptr(__model);
         return *__model;
       }