foo.cc: In function 'int main()':
foo.cc:8:10: error: could not convert 'huida.std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=<char, std::char_traits<char>, std::allocator<char> >(koulin)' from 'std::__cxx11::basic_string<char>' to 'bool'
  if(huida=koulin)cout<<"门打开了";
     ~~~~~^~~~~~~

自豪的采用jd5进行评测(github.com/masnn/jd5)