A few bugs/problems in IndexWith

[zverok]

A bunch of minor bugs/problems with IndexWith. (Maybe it would’ve been better to make a ticket for each, but I assume they all can be fixed together.)

Mostly related to autocorrect (other than the first one).

1. The cop doesn’t detect problems with numbered block parameters collection.to_h { [_1, something(_1)] }. Probably affects IndexBy, too.
2. Autocorrection: Produces invalid code when there is a braceless hash in to_h:
   a. code: collection.to_h { |x| [x, position: x, value: y] }.
   b. correction: index_with { |x| position: x, value: y }
   c. proper correction: index_with { |x| {position: x, value: y} }
3. Autocorrection: Ignores the simplification when value doesn’t depend on the key:
   a. code: KEYS.to_h { |key| [key, true] } (frequently used in producing some initial/default value hashes)
   b. correction: KEYS.index_with { |key| true }
   c. better correction: KEYS.index_with(true)
4. Incorrect correction when keys are only the first element of the array (probably shouldn’t suggest correction at all):

# sample data
SETTINGS = {validate: true, numeric: false, length: false}

# code that causes offense:
defaults = SETTINGS.to_h { |key,| [key, true] }
# => {validate: true, numeric: true, length: true}

# proposed correction:
defaults = SETTINGS.index_with { |key| [true] }
# => {[:validate, true] => true, [:numeric, false] => true, [:length, false] => true}

RuboCop version

$ bundle exec rubocop -V
1.64.1 (using Parser 3.3.3.0, rubocop-ast 1.31.3, running on ruby 2.7.8) [x86_64-linux]
  - rubocop-capybara 2.21.0
  - rubocop-factory_bot 2.26.1
  - rubocop-graphql 1.1.1
  - rubocop-performance 1.21.0
  - rubocop-rails 2.25.0
  - rubocop-rake 0.6.0
  - rubocop-rspec 3.0.1
  - rubocop-rspec_rails 2.30.0