I've tried to use ```typeof(t) is cast(t)null```, but compiler
exits with error and so this can't be used for checking this
issue.
The goal I with to achieve by this check - is to use template and
to assign value to variable basing on it's ability to accept null
as a value.
some testing code below.
```D
import std.stdio;
interface I1
{
}
class C1 : I1
{
}
struct S1
{
}
struct S2
{
int a=1;
}
void main()
{
auto c1 = new C1;
I1 i1 = c1;
auto s1 = S1();
auto s2 = S2();
static assert(typeof(c1).init is cast(typeof(c1)) null);
static assert(typeof(i1).init is cast(typeof(i1)) null);
static assert(typeof(s1).init is cast(typeof(s1)) null);
static assert(typeof(s2).init is cast(typeof(s2)) null);
static assert(int.init is cast(int) null);
}
```
