CodeLine Lex doesn't handle trailing if and unless

[schneems]

The assumption was that if and unless lines need to be paired with ends, but that's not true if it's trailing:

       +  end
       +  class Main
       +        @user_source_code = 'self' if @user_source_code == ''
       +    end
       +  end

[schneems]

irb(main):001:0> require 'ripper'
=> false
irb(main):002:0> pp Ripper.lex("puts 'lol' if foo")
[[[1, 0], :on_ident, "puts", CMDARG],
 [[1, 4], :on_sp, " ", CMDARG],
 [[1, 5], :on_tstring_beg, "'", CMDARG],
 [[1, 6], :on_tstring_content, "lol", CMDARG],
 [[1, 9], :on_tstring_end, "'", END],
 [[1, 10], :on_sp, " ", END],
 [[1, 11], :on_kw, "if", BEG|LABEL],
 [[1, 13], :on_sp, " ", BEG|LABEL],
 [[1, 14], :on_ident, "foo", CMDARG]]

[schneems]

I think that we can disambiguate a trailing end if it is a "BEG|LABEL" as a non-trailing end will just be a BEG

source = <<~EOM
  if bar; puts "lol"; end
EOM

pp Ripper.lex(source)
[[[1, 0], :on_kw, "if", BEG],
 [[1, 2], :on_sp, " ", BEG],
 [[1, 3], :on_ident, "bar", CMDARG],
 [[1, 6], :on_semicolon, ";", BEG],
 [[1, 7], :on_sp, " ", BEG],
 [[1, 8], :on_ident, "puts", CMDARG],
 [[1, 12], :on_sp, " ", CMDARG],
 [[1, 13], :on_tstring_beg, "\"", CMDARG],
 [[1, 14], :on_tstring_content, "lol", CMDARG],
 [[1, 17], :on_tstring_end, "\"", END],
 [[1, 18], :on_semicolon, ";", BEG],
 [[1, 19], :on_sp, " ", BEG],
 [[1, 20], :on_kw, "end", END],
 [[1, 23], :on_nl, "\n", BEG]]

source = <<~EOM
  foo = if bar; "lol"; end
EOM

pp Ripper.lex(source)
[[[1, 0], :on_ident, "foo", CMDARG],
 [[1, 3], :on_sp, " ", CMDARG],
 [[1, 4], :on_op, "=", BEG],
 [[1, 5], :on_sp, " ", BEG],
 [[1, 6], :on_kw, "if", BEG],
 [[1, 8], :on_sp, " ", BEG],
 [[1, 9], :on_ident, "bar", CMDARG],
 [[1, 12], :on_semicolon, ";", BEG],
 [[1, 13], :on_sp, " ", BEG],
 [[1, 14], :on_tstring_beg, "\"", BEG],
 [[1, 15], :on_tstring_content, "lol", BEG],
 [[1, 18], :on_tstring_end, "\"", END],
 [[1, 19], :on_semicolon, ";", BEG],
 [[1, 20], :on_sp, " ", BEG],
 [[1, 21], :on_kw, "end", END],
 [[1, 24], :on_nl, "\n", BEG]]