Some Nullable-related issue

[Denis Feklushkin]

Pavel Chebotarev found that this code causes error on DMD:

import std.typecons;

struct Atom
{
     Nullable!long a1;
     Nullable!long a2;
     Nullable!long a3;
     Nullable!long a4;
     Nullable!long a5;
     Nullable!long a6;
     Nullable!long a7;
     Nullable!long a8;
     Nullable!long a9;
     Nullable!long a10;
}

struct Molecule
{
     Nullable!Atom a1;
     Nullable!Atom a2;
     Nullable!Atom a3;
     Nullable!Atom a4;
}

struct Material
{
     Nullable!Molecule u1;
     Nullable!Molecule u2;
     Nullable!Molecule u3;
}

struct House
{
     Nullable!Material m1;
}

dmd bug01.d                                                       
                                                                   
                                         
/usr/include/dmd/phobos/std/traits.d(2810): Error: template 
instance 
`std.traits.RepresentationTypeTuple!(Material).Impl!(Atom, bool, 
bool)` recursive expansion

Probably, LDC is not affected, but currently we can't check this 
(and maybe LDC uses another version of Phobos and this is Phobos 
issue)