Creating a variable inside a function arguments

[Anmol444]

In the following code:

#include <iostream>                              // For stream I/O
using namespace std;

int function(int a)
{
	return a;
}

int main()
{
	function(int b);
}

Why is creating a variable inside the function argument list not allowed. Any reason other then for the language syntax or just for the language syntax?