Type annotations break function arguments coloration #312

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: https://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

With tree sitter enabled, adding type annotations to function arguments breaks argument coloration.

Steps to Reproduce

Add type annotations to a function argument

Expected behaviour:

Argument coloration should remain the same with or without a type annotation.

Actual behavior:

Argument coloration disappears, the argument is now of default text colour.

Reproduces how often:

Always.

Versions

Atom : 1.41.0
Electron: 4.2.7
Chrome : 69.0.3497.128
Node : 10.11.0
apm 2.4.3
npm 6.2.0
node 10.2.1 x64
atom 1.41.0
python 2.7.17rc1
git 2.20.1