[Fix #7680] Add new Lint/StructNewOverride cop

[ybiquitous]

Fix #7680

This adds a new Lint/StructNewOverride cop to check unexpected overrides of Struct original methods.

I originally planned to name it "Lint/StructOverride", but I think that disallowing all the overrides is too strict, so I rename it to Lint/StructNewOverride. I intend that this cop limits to overrides via arguments in Struct.new(...).

However, the cop name may need to be discussed more.

Furthermore, as I commented on #7680 (comment), it may need more discussion on whether the cop should check all the methods (from Object or Enumerable) or not.

---

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.

[ybiquitous]

By following #7680 (comment), I've mad the cop message milder via f10bc600aa3f96e962bce9b7d9d4822d2a48eb8a.

E.g.

:members member overrides Struct#members and it may be unexpected.

[bbatsov]

And then we can name this StructBuiltInMethodOverride which is more descriptive IMO.

[ybiquitous]

Thank you. I also think that StructBuiltInMethodOverride is easier to understand than StructNewOverride. 👍
I'll fix it.

[ybiquitous]

I assume that this cop detects some overrides by arguments of Struct.new, not normal overrides as follows:

Foo = Struct.new(:name) do
  def to_s
    name.to_s
  end
end

I'm a bit concerned that StructBuiltInMethodOverride may be considered as any overrides of the built-in methods. 🤔

[ybiquitous]

For example, StructBuiltInMethodOverrideByConstructor may be more descriptive but too long. 😓
I may think too much... Please give me any help! 🙏

[bbatsov]

Naming is hard! :D Let's keep the shorter name and down the road we can maybe extend this cop to cover dangerous overrides by explicit definitions as well.

[ybiquitous]

Make sense. Thanks! 👍

[bbatsov]

Apart from my small remarks - great work!

[ybiquitous]

I've addressed all the reviews. Please review again if you have time. 🙏

[bbatsov]

🚀