The following result doesn't make sense to me... how does
isInstanceOf return false?
```
import std.traits;
import std.stdio;
import std.typecons;
auto f(T)(T t){
return Nullable!T(t);
}
void main(){
auto f3 = f(3);
writeln(typeof(f3).stringof);
writeln(isInstanceOf!(Nullable, f3));
}
```
outputs
```
Nullable!int
false
```