Incorrect highlighting for nth-child selectors

[adamreisnz]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: http://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: http://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

Blue nth-child scope:

Orange nth-child scope:

Red ampersand scope:

Grey ampersand scope:

Steps to Reproduce

.SomeClass {
  &:nth-child(1), &:nth-child(2) {
    color: $colorRed;
  }
  &:nth-child(3) {
    color: $colorYellow;
  }
  &:nth-child(4), &:nth-child(5) {
    color: $colorGreen;
  }
}

Expected behavior: [What you expect to happen]
Consistent scoping

Actual behavior: [What actually happens]
Inconsistent scoping, see screenshot

Reproduces how often: [What percentage of the time does it reproduce?]
100%

Versions

Atom : 1.23.0-dev-9097c9ac2
Electron: 1.6.15
Chrome : 56.0.2924.87
Node : 7.4.0

apm 1.18.10
npm 3.10.10
node 6.9.5 x64
atom 1.23.0-dev-9097c9ac2
python 2.7.12
git 2.14.1

OS X

[adamreisnz]

There seem to be some more cases involving ampersand usage where selectors are no longer properly recognised: