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

[Dmitry Gutov]

On 14.10.2013 16:44, Stefan Monnier wrote:
> > So basically, I think we'd like to check if the token following POS is
> > either not "special", or if it is, it begins an expression.  Can we do
> > that?
>
> ...(+)  But it'll be more difficult to handle
> ...(++)
> since there's no space to use as "implicit method call infix operator".

No, space is significant(++), I'm not suggesting to revert the addition 
of the " @ " token. But we need a better predicate in 
`ruby-smie--args-separator-p' to check that the thing after POS is 
probably an argument. "Starts with a word character" is too narrow.

> (+) I don't see anything that would stop us.

How would that look?

(unless (member (save-excursion (ruby-smie--forward-token) '("]" "}" 
"end" "+" "-" "?" ":" ...)))

?

Can we extract the "prohibited" list from the already defined grammar?

Or should the check be more like "is the next token in 
`ruby-smie-grammar', and if yes, is its left priority more than ' @ 's 
right priority"?

(++)
>      method(arg1),
>            arg2
> or
>      method{arg1},
>            arg2
>

Both examples would result in syntax errors. The second one doubly so, 
since the first arg there is not a hash, but a block, and a block can 
only come after all other arguments.

Even if the first argument were {:a => 1, :b => 2}, actually, it won't 
work because "{" in this position is parsed as the beginning of a block 
(that means one of the examples I added is wrong, sorry!).

You've probably already found this, but on the off chance you haven't, 
here's its syntax in (incomplete, somewhat outdated, etc) BNF form: 
http://www.cse.buffalo.edu/~regan/cse305/RubyBNF.pdf

> +# Shouldn't "bar" be aligned with "foo"?  --Stef
>   if foo &&
>       bar
>   end

Maybe. Either option would be better than the current behavior. I've 
picked this one because the old engine indents it like so, and 
additional indentation of 2 (compared to the if body) would likely be 
more useful that 1, when reading the code.


> +# Shouldn't "arg2" be aligned with "!" rather than with "arg1"?  --Stef
>   method !arg1,
>           arg2

Yes, sorry. Fixed, and added a couple of new examples, like usual.