Problems with double && compilation

[junquanDong]

I have a puzzled question.
The && selector is not ideal when compiled.
Please see the code snippet.

Code:

[type=password]{
  .a{
    &&-b{
      color:red;
    }
  }
}

Compile Code:

[type=password] .a[type=password] .a-b {
  color: red;
}

preset:

[type=password] .a.a-b {
  color: red;
}