fn has_default_output(&self) -> bool {
        match self.fn_item.sig.output {
            ReturnType::Default => true,
            _ => false
        }
    }
/// check whether this function return ()
check whether this function return ()
check whether this function return ()
fn has_default_output(&self) -> bool {
        match self.fn_item.sig.output {
            ReturnType::Default => true,
            _ => false
        }
    }
fn has_default_output ( & self ) -> bool { match self . fn_item . sig . output { ReturnType :: Default => true , _ => false } }
check whether this function return ()
check whether this function return ()
&self