Currently, the following code:

import std.stdio;

struct S
{
   int x;
   this(this) { writeln("postblit"); }
   ~this() { writeln("dtor"); }
}

void main()
{
   S[] arr;
   arr ~= S();
}

outputs:

postblit
dtor

But it could have move semantics.  However, the runtime function which appends data does not know whether the given data to append is an rvalue or not.  For example, the following cannot have move semantics:

S s;
s.x = 1;
arr ~= s;
writeln(s.x);

So the compiler must give an additional flag (or call a separate runtime function) when appending an rvalue.  When the compiler does this, flip the bug to a druntime bug and assign it to me, and I'll fix the runtime.