Partial indentation of some nested calls raises an error in Style/FirstParameterIndentation

[awwaiid]

Ran into an exception raised by Style/FirstParameterIndentation in some badly indented code. I narrowed it down quite a bit (though this might not be completely minimal. I might look into a fix, but wanted to record the issue in case I don't get to it.

bwilcox@koopa:~/tmp/rubocop$ ./bin/rubocop -v                                 [master]
0.32.1
bwilcox@koopa:~/tmp/rubocop$ cat failing_rubocop.rb                           [master]
foo(
 bar(
  7
))
bwilcox@koopa:~/tmp/rubocop$ ./bin/rubocop -d failing_rubocop.rb              [master]
Inspecting 1 file
Scanning /home/bwilcox/tmp/rubocop/failing_rubocop.rb
For /home/bwilcox/tmp/rubocop: configuration from /home/bwilcox/tmp/rubocop/.rubocop.yml
Inheriting configuration from /home/bwilcox/tmp/rubocop/.rubocop_todo.yml
Default configuration from /home/bwilcox/tmp/rubocop/config/default.yml
Inheriting configuration from /home/bwilcox/tmp/rubocop/config/enabled.yml
Inheriting configuration from /home/bwilcox/tmp/rubocop/config/disabled.yml
An error occurred while Style/FirstParameterIndentation cop was inspecting /home/bwilcox/tmp/rubocop/failing_rubocop.rb.
undefined method `parent' for nil:NilClass
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/style/first_parameter_indentation.rb:42:in `message'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/cop.rb:162:in `add_offense'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/mixin/autocorrect_alignment.rb:27:in `block in check_alignment'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/mixin/autocorrect_alignment.rb:16:in `each'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/mixin/autocorrect_alignment.rb:16:in `check_alignment'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/style/first_parameter_indentation.rb:35:in `on_send'
(eval):5:in `block (2 levels) in on_send'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/commissioner.rb:92:in `with_cop_error_handling'
(eval):4:in `block in on_send'
(eval):2:in `each'
(eval):2:in `on_send'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/ast-2.0.0/lib/ast/processor.rb:239:in `process'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/ast-2.0.0/lib/ast/processor.rb:255:in `block in process_all'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/ast-2.0.0/lib/ast/processor.rb:254:in `map'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/ast-2.0.0/lib/ast/processor.rb:254:in `process_all'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/parser-2.2.2.6/lib/parser/ast/processor.rb:143:in `on_send'
(eval):9:in `on_send'
/home/bwilcox/.rvm/gems/ruby-2.0.0-p451/gems/ast-2.0.0/lib/ast/processor.rb:239:in `process'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/commissioner.rb:52:in `investigate'
/home/bwilcox/tmp/rubocop/lib/rubocop/cop/team.rb:33:in `inspect_file'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:135:in `inspect_file'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:106:in `block in do_inspection_loop'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:100:in `loop'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:100:in `do_inspection_loop'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:78:in `process_file'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:53:in `block in inspect_files'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:51:in `each'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:51:in `inspect_files'
/home/bwilcox/tmp/rubocop/lib/rubocop/runner.rb:30:in `run'
/home/bwilcox/tmp/rubocop/lib/rubocop/cli.rb:26:in `run'
./bin/rubocop:13:in `block in <main>'
/home/bwilcox/.rvm/rubies/ruby-2.0.0-p451/lib/ruby/2.0.0/benchmark.rb:296:in `realtime'
./bin/rubocop:12:in `<main>'
C

Offenses:

failing_rubocop.rb:1:1: C: Style/Encoding: Missing utf-8 encoding comment.
foo(
^
failing_rubocop.rb:2:2: C: Style/FirstParameterIndentation: Indent the first parameter one step more than the start of the previous line.
 bar(
 ^^^^
failing_rubocop.rb:4:1: C: Style/ClosingParenthesisIndentation: Indent ) the same as the start of the line where ( is.
))
^

1 file inspected, 3 offenses detected

1 error occurred:
An error occurred while Style/FirstParameterIndentation cop was inspecting /home/bwilcox/tmp/rubocop/failing_rubocop.rb.
Errors are usually caused by RuboCop bugs.
Please, report your problems to RuboCop's issue tracker.
Mention the following information in the issue report:
0.32.1 (using Parser 2.2.2.6, running on ruby 2.0.0 x86_64-linux)
Finished in 0.018936341 seconds