`unused variable` warning is reported when grammer definition includes `*` qualifier

[taichi-ishitani]

Ruby reports unused variable warning for source file generated from the grammar definition includes * qualifier.

How to reproduce:

Give the source file geneated from the grammer definition below to Ruby with -W option.

class TestParser
options no_result_var

rule
 root
 : 'a' 'b'*

$ racc --version
racc version 1.8.1
$ racc test.y
$ ruby -W test.tab.rb
test.y:8: warning: assigned but unused variable - result
test.y:8: warning: assigned but unused variable - result

Ruby code below is geneated from the the above grammer definition.

#
# DO NOT MODIFY!!!!
# This file is automatically generated by Racc 1.8.1
# from Racc grammar file "test.y".
#

require 'racc/parser.rb'
class TestParser < Racc::Parser
##### State transition tables begin ###

racc_action_table = [
 2, 3, 4, 6, 4 ]

racc_action_check = [
 0, 1, 2, 3, 4 ]

racc_action_pointer = [
 -2, 1, -1, 3, 1, nil, nil, nil ]

racc_action_default = [
 -4, -4, -1, -4, -1, -3, 8, -2 ]

racc_goto_table = [
 5, 1, 7 ]

racc_goto_check = [
 2, 1, 2 ]

racc_goto_pointer = [
 nil, 1, -2 ]

racc_goto_default = [
 nil, nil, nil ]

racc_reduce_table = [
 0, 0, :racc_error,
 0, 6, :_reduce_1,
 2, 6, :_reduce_2,
 2, 5, :_reduce_none ]

racc_reduce_n = 4

racc_shift_n = 8

racc_token_table = {
 false => 0,
 :error => 1,
 "a" => 2,
 "b" => 3 }

racc_nt_base = 4

racc_use_result_var = false

Racc_arg = [
 racc_action_table,
 racc_action_check,
 racc_action_default,
 racc_action_pointer,
 racc_goto_table,
 racc_goto_check,
 racc_goto_default,
 racc_goto_pointer,
 racc_nt_base,
 racc_reduce_table,
 racc_token_table,
 racc_shift_n,
 racc_reduce_n,
 racc_use_result_var ]
Ractor.make_shareable(Racc_arg) if defined?(Ractor)

Racc_token_to_s_table = [
 "$end",
 "error",
 "\"a\"",
 "\"b\"",
 "$start",
 "root",
 "\"-many@b\"" ]
Ractor.make_shareable(Racc_token_to_s_table) if defined?(Ractor)

Racc_debug_parser = false

##### State transition tables end #####

# reduce 0 omitted

module_eval(<<'.,.,', 'test.y', 7)
 def _reduce_1(val, _values)
 result = val[1] ? val[1].unshift(val[0]) : val
 end
.,.,

module_eval(<<'.,.,', 'test.y', 7)
 def _reduce_2(val, _values)
 result = val[1] ? val[1].unshift(val[0]) : val
 end
.,.,

# reduce 3 omitted

def _reduce_none(val, _values)
 val[0]
end

end # class TestParser