Is there a simple way to check if value is null for every case?

[SG via Digitalmars-d-learn]

Hi again,

The code below works for some cases but not for the Nullable!Type.
A way to fix it should be check the type and use ".isNull" for 
Nullabe!Type. But is there a simple way to test if value is null 
for every case?


import std.stdio, std.typecons, std.variant, std.conv;

bool foo(T)(T t){
    return (t is null);
}

class S{
    Nullable!int i;
}

void main(){
    string x = "a";
    writeln(x is null," - " ,x.foo);

    string y = null;
    writeln(y is null," - ", y.foo);

    auto z = null;
    writeln(z is null," - ", z.foo);


    S s = new S();
    writeln(s.i.isNull); // Ok

    //writeln(s.i is null); // Error
    //s.i.foo(2); // Error
}