ios - UIView override func touchesBegan default stub throwing error -

xcode 8.3.3 w/ swift 3

import uikit  class myview: uiview { override func touchesbegan(_ touches: set<uitouch>, event: uievent?) {  }  override func touchesmoved(_ touches: set<uitouch>, event: uievent?) {  }  override func touchesended(_ touches: set<uitouch>, event: uievent?) {  }  override func touchescancelled(_ touches: set<uitouch>?, event: uievent?) {     // don't forget add "?" after set<uitouch> } } 

all 4 functions throwing error: "cannot specialize non generic type "set". same code in beta 6 of xcode 9 doesn't have same issue.