Value category is a property of an expression in C++

The code below prints l-value:

#include <iostream>

namespace
{
    void foo(const int&)
    {
        std::cout << "const l-value" << std::endl;
    }

    void foo(int&)
    {
        std::cout << "l-value" << std::endl;
    }

    void foo(int&&)
    {
        std::cout << "r-value" << std::endl;
    }
}
int main()
{
    int&& x = 1;

    foo(x);

    return 0;
}

The type of variable x is int&&, but the value category of expression x is l-value.

That is why we need std::forward:

template <typename T>
void deduce(T&& x)
{
    //at this point expression x is l-value,
    //because it is a named variable.
    foo(std::forward<T>(x));
}

int main()
{
    //we pass r-value
    deduce(1);

    return 0;
}

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