util/generic/variant.h


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#pragma once

#include "hash.h" 

#include <variant> 

template <class... Ts>
struct THash<std::variant<Ts...>> { 
public:
    size_t operator()(const std::variant<Ts...>& v) const noexcept { 
        return CombineHashes( 
            IntHash(v.index()), 
            v.valueless_by_exception() ? 0 : std::visit([](const auto& value) { return ComputeHash(value); }, v)); 
    }
};

template <>
struct THash<std::monostate> { 
public:
    constexpr size_t operator()(std::monostate) const noexcept { 
        return 1;
    }
};