Null assignment in class fields

[varivera]

In
void m(){
v = w;
}

Should we assume that w is not null at that point? If so, after execution it should be
v:w (v is aliased to w)
If not, it should be
{v:{w, null}}(v might be aliased to w or null: as we do not have information about w)

[varivera]

For now, we are not assuming null. Meaning, no variable can be assigned to null