[tree-sitter] "then" keyword is not recognized, and 'case' statement is not folded

[t9md]

Prerequisites

• [x] 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

I'm trying to use Tree-sitter parser and found some issues.

• "then" keyword and "puts" method are not correctly highlighted.
• The "case" statement is not foldable whether I use "then" or not.
• If I add "then" keyword afterward to the already completed case-statement, syntax color would be broken.

Steps to Reproduce

With sample code below

def test(grade)

  if true
    puts "hello"
  elsif false
    puts "hello"
  else
    puts "hi"
  end

  case grade
  when "A", "A+" then
    puts 'Well done!'
  when "B", "B+" then
    puts 'Try harder!'
  when "C" then
    puts 'You need help!!!'
  else
    puts "You just making it up!"
  end

end

test "A"

TextMate

Tree-sitter: See syntax color of 'then' and also foldable marker on the gutter.

Tree-sitter: GIF below is when I add then to the case-statement is Tree-sitter

Expected behavior: [What you expect to happen]

Tree-sitter parser works as accurately as TextMate parser.

Actual behavior: [What actually happens]

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

Versions

Atom    : 1.31.0-beta1
Electron: 2.0.7
Chrome  : 61.0.3163.100
Node    : 8.9.3

[Ben3eeE]

/cc: @maxbrunsfeld

[t9md]

Ignore "puts" part, it seems to be OK(no problem).