  UTF16Ref getUTF16Ref(llvh::SmallVectorImpl<char16_t> &allocator) const {
    assert(allocator.empty() && "Shouldn't use a non-empty allocator");
    return getUTF16Ref(allocator, false);
  }
  UTF16Ref getUTF16Ref(llvh::SmallVectorImpl<char16_t> &allocator) const {
    assert(allocator.empty() && "Shouldn't use a non-empty allocator");
    return getUTF16Ref(allocator, false);
  }