Style/ParallelAssignment breaks in combination with splat operator #13505
Description
Style/ParallelAssignment breaks for the following valid bit of Ruby code:
a, b, * = [1, 2, 3]
Error: An error occurred while Style/ParallelAssignment cop was inspecting ...
Expected behavior
Would expect it to not crash, just like it doesn't for the following, equivalent, bit of Ruby code:
a, b, = [1, 2, 3]
Actual behavior
rubocop -d --only Style/ParallelAssignment test.rb
For ...: Default configuration from /Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/config/default.yml
Use parallel by default.
Skipping parallel inspection: only a single file needs inspection
Inspecting 1 file
Scanning .../test.rb
An error occurred while Style/ParallelAssignment cop was inspecting .../test.rb:1:0.
undefined method `splat_type?' for nil
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/style/parallel_assignment.rb:64:in `any?'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/style/parallel_assignment.rb:64:in `allowed_lhs?'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/style/parallel_assignment.rb:36:in `on_masgn'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:107:in `public_send'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:107:in `block (2 levels) in trigger_responding_cops'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:171:in `with_cop_error_handling'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:106:in `block in trigger_responding_cops'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:105:in `each'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:105:in `trigger_responding_cops'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:69:in `on_masgn'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-ast-1.36.1/lib/rubocop/ast/traversal.rb:20:in `walk'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/commissioner.rb:87:in `investigate'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/team.rb:174:in `investigate_partial'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cop/team.rb:108:in `investigate'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:349:in `block in inspect_file'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:348:in `each'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:348:in `flat_map'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:348:in `inspect_file'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:291:in `block in do_inspection_loop'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:325:in `block in iterate_until_no_changes'
<internal:kernel>:187:in `loop'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:318:in `iterate_until_no_changes'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:287:in `do_inspection_loop'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:168:in `block in file_offenses'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:193:in `file_offense_cache'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:167:in `file_offenses'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:158:in `process_file'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:139:in `block in each_inspected_file'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:138:in `each'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:138:in `reduce'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:138:in `each_inspected_file'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:124:in `inspect_files'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/runner.rb:77:in `run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/command/execute_runner.rb:26:in `block in execute_runner'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/command/execute_runner.rb:52:in `with_redirect'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/command/execute_runner.rb:25:in `execute_runner'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/command/execute_runner.rb:17:in `run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/command.rb:11:in `run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli/environment.rb:18:in `run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli.rb:122:in `run_command'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli.rb:129:in `execute_runners'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli.rb:51:in `block in run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli.rb:81:in `profile_if_needed'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/lib/rubocop/cli.rb:43:in `run'
/Users/work/.rbenv/versions/3.3.6/lib/ruby/gems/3.3.0/gems/rubocop-1.69.0/exe/rubocop:19:in `<top (required)>'
/Users/work/.rbenv/versions/3.3.6/bin/rubocop:25:in `load'
/Users/work/.rbenv/versions/3.3.6/bin/rubocop:25:in `<main>'
Steps to reproduce the problem
Save the following Ruby code as test.rb:
a, b, * = [1, 2, 3]
Then run rubocop -d --only Style/ParallelAssignment test.rb.
RuboCop version
1.69.0 (using Parser 3.3.6.0, rubocop-ast 1.36.1, analyzing as Ruby 2.7, running on ruby 3.3.6) [arm64-darwin23]