복사생성자

class Fraction
{
private:
	int m_numerator;
	int m_denominator;
public:
	Fraction(int num = 0, int den = 1)
		:m_numerator(num), m_denominator(den)
	{
		assert(den != 0);
	}
	Fraction(Fraction& fraction)
		:m_numerator(fraction.m_numerator), m_denominator(fraction.m_denominator)
	{
		cout << "copy constructor called" << endl;
	}
	friend std::ostream& operator<<(std::ostream& out, const Fraction& f)
	{
		cout << f.m_numerator << "/" << f.m_denominator << endl;
		return cout;
	}
};
int main()
{
	Fraction frac(3, 5);
	Fraction fr_copy( Fraction(3,10) );

	cout << frac << " " << fr_copy << endl;


	return 0;
}

복사생성자에서 const키워드가 없을때 오류가 발생하는 이유가 궁금합니다.

Fraction fr_copy( Fraction(3,10) );

위 부분에서

Error C2558 class 'Fraction': no copy constructor available or copy constructor is declared 'explicit'

이렇게 에러가 발생합니다

Fraction(const Fraction& fraction)
    : m_numerator(fraction.m_numerator), m_denominator(fraction.m_denominator)
{
    cout << "copy constructor called" << endl;
}