Can i not declare a non-static const data member?

Code:
class A
{	
	public:
	const int x;	
	A()
	{
		x = 10;            
	}
};

int main()
{
	return 0;
}
problem is here is, compiler allows me to declare a non-static const data member, meaning i can somehow use it. But how do i initialize it?

Constructor Initialization fails bcoz compiler prevents assignment to a const data member,
and initialization at declaration is prevented by ISO C++ std. that says i cannot initialize data members inside a class until they are static const

so, why even the declaration of non-static const data member has been allowed by the compiler, when there is no way i can initialize it ?