More powerful SlicingWithRange

[zverok]

Supports any expression as start index (only int previously), as noticed here: #7921 (comment).
Still correctly ignores startless range.

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• [ ] Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[marcandre]

I think either (...)or !nil? will do, right? Which do you find clearer?

[koic]

That suggestion fine to me. @zverok Can you update this one?

diff --git a/lib/rubocop/cop/style/slicing_with_range.rb b/lib/rubocop/cop/style/slicing_with_range.rb
index 1611b61a4..de3769d9b 100644
--- a/lib/rubocop/cop/style/slicing_with_range.rb
+++ b/lib/rubocop/cop/style/slicing_with_range.rb
@@ -19,7 +19,7 @@ module RuboCop

         MSG = 'Prefer ary[n..] over ary[n..-1].'

-        def_node_matcher :range_till_minus_one?, '(irange (...) (int -1))'
+        def_node_matcher :range_till_minus_one?, '(irange !nil? (int -1))'

         def on_send(node)
           return unless node.method?(:[]) && node.arguments.count == 1

[zverok]

@koic np, I've updated the PR. I liked (...) slightly better, but that's not something to spend time fighting about :)

(BTW, I believe that GitHub now allows maintainers to introduce such small changes themselves right on the web. Not that I am too lazy to do it myself, just interesting what the ethics around this would be, in the future.)

[bbatsov]

Thanks!