Add specs for reserved keywords

[amomchilov]

Add specifications for all the reserved keywords, documenting which of them can be used as:

1. local variables
2. instance variables
3. global variables
4. positional parameter names
5. keyword parameter names
6. method names

[amomchilov]

TODO: It would be nice to have one canonical list that can be used in all these places:

1. spec/ruby/language/hash_spec.rb
2. spec/ruby/language/reserved_keywords.rb
3. lib/prism/translation/ripper.rb
4. Ideally, it would also be nice to generate doc/keywords.rdoc from that list, to ensure that all keywords are documented.

Where should such a canonical list live?

[eregon]

There is no way to avoid duplication there, since it's files in different repositories.
So for ruby/spec let's have it as a new file under language/fixtures.
I think a %w[] array would be nice for this BTW.

FWIW in ruby/ruby there is also defs/keywords.

[amomchilov]

Good call, done: 0f54929 (#1187)

[eregon]

Adding these specs seems good but they should match the existing style and structure of ruby/spec, I'll review in more details once it does.

[eregon]

Suggested change

	keywords.each do |kw|
	keywords.each do |name|

kw feels too confusing here, especially since there is a spec about keyword arguments below.
Since we are mostly testing names for variables/methods, name seems clearer in usages.

[amomchilov]

Mmmmm I disagree, in a spec focused on describing the behaviour of keywords, I would expect "keyword" to a be prominent term. It's an overloaded term, but that's just how Ruby is already. Perhaps keyword is better than kw?

Anyway, I renamed to name

[eregon]

Thanks for taking another stab at this.
Could you address my comments? Then I think it should be good to merge.

[amomchilov]

OK, I think that's everything addressed.

I kept the history in tract to make it easier to review, but I'll squash and rebase before merging

[amomchilov]

Mmmmm I disagree, in a spec focused on describing the behaviour of keywords, I would expect "keyword" to a be prominent term. It's an overloaded term, but that's just how Ruby is already. Perhaps keyword is better than kw?

Anyway, I renamed to name