why @property cannot be pass as ref ?

[ChangLong]

On Wednesday, 20 December 2017 at 18:43:21 UTC, Ali Çehreli wrote:
> Thanks to Mengü for linking to that section. I have to make 
> corrections below.
>
> Ali


Thanks for explain, Ali And Mengu.

What I am try to do is implement a unique data type. (the 
ownership auto moved into new handle)

consider this code:

import std.stdio;

struct S {
         @disable this(this);
     void* socket;
     this (void* i) {
         socket = i;
     }

     void opAssign()(auto ref S s ){
         socket = s.socket ;
         s.socket = null ;
     }

     @nogc @safe
     ref auto byRef() const pure nothrow return
     {
         return this;
     }
}


void main() {
     static __gshared size_t socket;
     auto lvalue = S(&socket);   // pass rvalue into lvalue, 
working
     S l2 =  void;
     l2 = lvalue;        // pass lvalue into lvalue, working
     auto l3 = l2.byRef; // pass lvalue into lvalue, not working
}



I can not assign  l2 to l3 because "Error: struct app.S is not 
copyable because it is annotated with @disable", but it working 
if I init l3 with void.