Postblit isn't called on rvalue return

[Sebastian Graf]

For this program:

     import std.stdio;

     struct S
     {
         ubyte* b;
         ubyte buf[128];

         this(this)
         {
             writeln("postblit");
         }
     }

     auto ref makeS()
     {
         S s;
         s.b = s.buf;
         writeln("made S at ", cast(void*)&s, ", s.b == ", s.b);
         return s;
     }

     void main()
     {
         S s = makeS();
         writeln("got back S at ", cast(void*)&s, ", s.b == ", 
s.b);
     }

I get

     made S at 18FC64, s.b == 18FC68
     got back S at 18FCF4, s.b == 18FC68

as output for dmd 2.062. Patching s.b to point into the newly 
allocated struct in postblit is crucial here, but it seems like 
the postblit constructor isn't called, nor is there any attempt 
to optimize away the temporary in `makeS()` even with -O.
Is this is a bug or am I doing something wrong?