Skip to content

Use an alias to boost::variant instead of wrapping the type #2

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
MakersF wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Use an alias to boost::variant instead of wrapping the type #2

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
77 changes: 4 additions & 73 deletions include/resilient/detail/variant_boost.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -35,28 +35,9 @@ class IsType
}
};

template<typename Variant>
struct as_boost_variant
{
using type = same_const_ref_as_t<Variant, typename std::decay_t<Variant>::ImplVariant>;
};

template<typename Variant>
using as_boost_variant_t = typename as_boost_variant<Variant>::type;

// Allow to access the Failable as if it was a varian, so that all the variant functions can be used
template<typename Variant>
as_boost_variant_t<Variant> get_boost_variant(Variant&& v)
{
return move_if_not_lvalue<Variant>(v.d_data);
}

template<typename Q>
using if_is_default_constructible = std::enable_if_t<std::is_default_constructible<Q>::value>;


template<typename ...Types>
class Variant;// Forward declare so that we can define is_variant before the implementation
using Variant = boost::variant<Types...>;


template<typename T>
Expand All @@ -67,56 +48,6 @@ struct is_variant<Variant<Types...>> : std::true_type {};
template<typename Q>
using if_is_variant = std::enable_if_t<is_variant<std::decay_t<Q>>::value, void*>;

template<typename Q>
using if_is_not_variant = std::enable_if_t<not is_variant<std::decay_t<Q>>::value, void*>;

template<typename ...Types>
class Variant
{
// wrap boost variant, providing a more c++17 similar interface.
public:
template<typename U = argpack_element_t<0, Types...>,
typename = if_is_default_constructible<U>>
Variant() {} // Use a template parameter U so that the evaluation is postponed
// until instantiation

template<typename Other, if_is_variant<Other> = nullptr>
Variant(Other&& other)
: d_data(move_if_not_lvalue<Other>(other.d_data)) {}

template<typename Other, if_is_not_variant<Other> = nullptr>
Variant(Other&& other)
: d_data(std::forward<Other>(other)) {}

template<typename Other, if_is_variant<Other> = nullptr>
Variant& operator=(Other&& other)
{
d_data = move_if_not_lvalue<Other>(other.d_data);
return *this;
}

template<typename Other, if_is_not_variant<Other> = nullptr>
Variant& operator=(Other&& other)
{
d_data = std::forward<Other>(other);
return *this;
}

private:
using ImplVariant = boost::variant<Types...>;
ImplVariant d_data;

template<typename ...OtherTypes>
friend class Variant;

template<typename Variant>
friend struct as_boost_variant;

template<typename Variant>
friend as_boost_variant_t<Variant> get_boost_variant(Variant&& f);

};

// Visitor which forwards the value based on the ref-ness of the owning variant
template<typename Visitor, typename Variant>
struct RvalueForwardingVisitor
Expand All @@ -136,7 +67,7 @@ struct RvalueForwardingVisitor
template<typename T, typename Variant, if_is_variant<Variant> = nullptr>
bool holds_alternative(Variant&& variant) // TODO make it fail to compile if the variant can not hold T
{
return boost::apply_visitor(IsType<T>(), get_boost_variant(std::forward<Variant>(variant)));
return boost::apply_visitor(IsType<T>(), std::forward<Variant>(variant));
}

#if BOOST_STRICT_GET_NO_RVAL_SUPPORT
Expand All @@ -155,7 +86,7 @@ auto get(Variant&& variant) -> same_const_ref_as_t<Variant, T>
// Put boost::strict_get in the scope and use the unscoped call so that the overload we defined can be found
using boost::strict_get;
using resilient::detail::strict_get;
return strict_get<T>(get_boost_variant(std::forward<Variant>(variant)));
return strict_get<T>(std::forward<Variant>(variant));
}

template<typename Visitor, typename Variant, if_is_variant<Variant> = nullptr>
Expand All @@ -164,7 +95,7 @@ decltype(auto) visit(Visitor&& visitor, Variant&& variant)
// Boost does not support r-value visitors or variants in apply_visitor.
// We wrap the visitor so that we do the forwarding.
RvalueForwardingVisitor<Visitor, Variant> wrapper{visitor};
return boost::apply_visitor(wrapper, get_boost_variant(variant));
return boost::apply_visitor(wrapper, variant);
}

}
Expand Down