The third patch demonstrates how it's possible to close bug#67036
that was impossible to fix without more general changes in treesit.el.

The problem is that e.g. Ruby parser to such text:

  hash[:key]

produces such syntax tree:

  (element_reference object: (identifier) [ (simple_symbol) ])

so when point is on [ then 'M-C-f' can't move to ].

This is fixed now by the third patch: