splat behavior investigation

2.2.0 :001 > class Array
2.2.0 :002?>   def to_a
2.2.0 :003?>     raise
2.2.0 :004?>     end
2.2.0 :005?>   end
 => :to_a
2.2.0 :006 > *[12]
(irb):3:in `to_a': unhandled exception
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:190:in `buf_input'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:103:in `getc'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/slex.rb:205:in `match_io'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/slex.rb:75:in `match'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:282:in `token'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:264:in `lex'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:235:in `block (2 levels) in each_top_level_statement'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `loop'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `block in each_top_level_statement'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `catch'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `each_top_level_statement'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:485:in `eval_input'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:395:in `block in start'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:394:in `catch'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:394:in `start'
        from /home/petruchito/.rvm/rubies/ruby-2.2.0/bin/irb:11:in `<main>'