foo.cc:8:11: error: declaration of 'class T'
  template<typename T>
           ^
foo.cc:4:10: error:  shadows template parm 'class T'
 template<typename T>
          ^
foo.cc:10:11: error: declaration of 'class T'
  template<typename T>
           ^
foo.cc:4:10: error:  shadows template parm 'class T'
 template<typename T>
          ^

自豪的采用 HydroJudger 进行评测(github.com/hydro-dev/HydroJudger)