d置器的统调,也可以

void assumedLength(S)(ref S slice, size_t length) {
    if(slice.length >= length)
        slice.length = length;
    else
        assert(false, "Let's not corrupt memory today.");
}

void main() {
  auto arr = [ 1, 2, 3 ];
  arr.assumedLength = 2;
  writeln(arr);
}