//unsafe code propagation rule
rule: (X: function, Y: function)
case X call Y, -X tag suppress(unsafe_propagation_warning)
    {
        warning Y tag unsafe -> X tag unsafe
        message "safe function should not call unsafe code"
    }

//bugs propagation rule
rule: (X: function, Y: function)
case X call Y, - X tag suppress(bugs_propagation_warnings)
    {
        warning Y tag bug(no(No)) -> X tag bug(no(No))
        message "Function should declare bugs it aware of"
    }

testfunc3 = function: (a: num, b: num)->num,unsafe, bug(no(1273)) //function tags list
{
        x = a+b: num;
        y = a - b: num;
        
        (x + y) / 2;
}

testfunc2 = function: (a: num)->bool // because of testfunc3 marked as unsafe code,
                                      // testfunc2 should be marked so too
,suppress(bugs_propagation_warnings), suppress(unsafe_propagation_warning)
 
{
        b = testfunc3(a+1, a-1): num;
        (b==0);
}