Style/HashAsLastArrayItem copy with style "no_braces" can result in invalid code

[wcmonty]

Expected behavior

Using Style/HashAsLastArrayItem with EnforcedStyle: no_braces should yield valid Ruby code when there are duplicate Hashes in the array. This is similar to #8323, but has not been fully resolved when there are identical hashes in the array.

Actual behavior

The cop is not safe and results in invalid Ruby code.

Steps to reproduce the problem

# .rubocop.yml
AllCops:
  NewCops: enable

Style/HashAsLastArrayItem:
  EnforcedStyle: no_braces

# hash_as_last_array_item.rb before
# frozen-string-literal: true

# Note that the hashes are identical
a = [
  {
    foo: :bar,
  },
  {
    foo: :bar
  }
]

pp a

$ ruby hash_as_last_array_item.rb
[{:foo=>:bar}, {:foo=>:bar}]

$ rubocop -a hash_as_last_array_item.rb
Inspecting 1 file
E

Offenses:

hash_as_last_array_item.rb:5:3: C: [Corrected] Style/HashAsLastArrayItem: Omit the braces around the hash.
  { ...
  ^
hash_as_last_array_item.rb:6:14: C: [Corrected] Style/TrailingCommaInHashLiteral: Avoid comma after the last item of a hash.
    foo: :bar,
             ^
hash_as_last_array_item.rb:7:3: E: Lint/Syntax: unexpected token tCOMMA
(Using Ruby 2.4 parser; configure using TargetRubyVersion parameter, under AllCops)
  ,
  ^
hash_as_last_array_item.rb:8:3: C: [Corrected] Style/HashAsLastArrayItem: Omit the braces around the hash.
  { ...
  ^

1 file inspected, 4 offenses detected, 3 offenses corrected

# hash_as_last_array_item.rb after
# frozen-string-literal: true

a = [

    foo: :bar
  ,

    foo: :bar

]

pp a

$ ruby hash_as_last_array_item.rb
hash_as_last_array_item.rb:7: syntax error, unexpected ',', expecting ']'
hash_as_last_array_item.rb:11: syntax error, unexpected ']', expecting end-of-input

RuboCop version

$ rubocop -v
0.89.0