bug#15594: trunk r114639: * lisp/progmodes/ruby-mode.el (ruby-smie-grammar): Add rule for paren-free

[Dmitry Gutov <dgutov@yandex.ru>]

On 21.10.2013 17:25, Stefan Monnier wrote:
>>> Calling ruby-smie--forward-token is a bit dangerous since that function
>>> might itself be called from ruby-smie--forward-token.  It might work,
>>> but you'll have to think hard about why an inf-loop is not possible.
>> Hopefully because both `ruby-smie--forward-token' and
>> ruby-smie--backward-token' would only call `ruby-smie--forward-token', and
>> only when (> pos (point)), IOW there has to be some whitespace skipping done
>> between the recursive calls.
>
> Only recursing in one direction (only forward or only backward) is
> a good way to guarantee progress, indeed.  But currently
> ruby-smie--implicit-semi-p calls ruby-smie--backward-token, so beware.

That's a good point. And this would probably be more expensive approach, 
so I went with local search, for now.