cargo check false positive

pub struct MyStruct {
    num: i32
}

impl MyStruct {

    // setting to "pub", makes the warning disappear
    fn new() -> MyStruct {
        MyStruct { num : 2 }
    }

    pub fn add_num(&self, num: i32) -> i32 {
        self.num + num
    }
}

mod test {
    #[test]
    fn test_1() {
        use crate::MyStruct;
        let s = MyStruct::new();
        assert_eq!(4, s.add_num(2));
    }
}


----

$ rustc --version
rustc 1.32.0-nightly (4a45578bc 2018-12-07)

$ cargo check 
    Checking test2018 v0.1.0 (/home/user/tmp/test2018)
warning: method is never used: `new`
 --> src/lib.rs:7:5
  |
7 |     fn new() -> MyStruct {
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(dead_code)] on by default