new_contents: #! /usr/bin/env python
  
  from __future__ import absolute_import
  
  import json
  import re
  import os
  import logging
  from validator import Validator
  from validator.utils import find_file
  
  
  PAT = re.compile('\s+-->\s(?P<fname>.*?):(?P<lnum>\d+):(?P<col>\d+)')
  
  logger = logging.getLogger('validator')
  
  
  class Cargo(Validator):
      __filetype__ = 'rust'
  
      instant = False
      checker = 'cargo'
      args = 'check --color never'
  
      def parse_loclist(self, loclist, bufnr):
          logger.info('parse input = %s', [self, loclist, bufnr])
          lists = []
          j = 0
          for i, l in enumerate(loclist):
              r = PAT.match(l)
              if r:
                  j += 1
                  msg = r.groupdict()
                  text = loclist[i - 1] if i > 0 else ''
                  ty = 'E' if text.startswith('error') else 'W'
                  loc = self.compose_loc(j, bufnr, ty, text)
                  loc.update(msg)
                  lists.append(loc)
          logger.info(lists)
          return json.dumps(lists)
  
      def cmd(self, fname):
          return '{} {}'.format(self.binary, self.args)
  
      @property
      def cwd(self):
          return os.path.dirname(find_file('Cargo.toml'))
  
subject: Add rust lint