ref auto getRange() return scope move struct ?

[Newbie2019 via Digitalmars-d-learn]

I has this simple function has some memory bugs:

-------
struct TreeRange {
        @disable this() ;
        @disable this(this) ;
}
struct Tree {
        ref auto getRange() return scope {
                return TreeRange!T(_root);
        }
}
Tree tree;
auto range = tree.getRange();
------
when I trace the issue, I find the address for TreeRange is 
moved.  it TreeRange.__ctor the address is 0x7ffeefbfd168,   but 
"auto range = tree.getRange();" address is 0x7ffeefbfd420


How to prevent this struct move in this case ?