static void HandleReturn(Vm vm)
{
// SLOW: maybe there's a faster way to manipulate the stack here?
var result = vm.stack.PopTop ();
var maybeRa = vm.stack.PopTop ();
if (maybeRa.Kind == Value.Kinds.ReturnAddress) {
vm.ApplyReturnAddress (maybeRa.ReturnAddressValue);
} else {
Utils.Panic ();
}
vm.stack.Push (result);
}