False positive in unsafe_vector_initialization: nonintegral vector element type

[dtolnay]

unsafe fn f<T: Copy, R: std::io::Read>(len: usize, io: R) -> Result<Vec<T>, ()> {
    let mut vec = Vec::<T>::with_capacity(len);
    vec.set_len(len);

    /* io.read_exact... */

    Ok(vec)
}

error: unsafe vector initialization
 --> src/main.rs:3:5
  |
2 |     let mut vec = Vec::<T>::with_capacity(len);
  |                   ---------------------------- help: consider replace allocation with: `vec![0; len]`
3 |     vec.set_len(len);
  |     ^^^^^^^^^^^^^^^^
  |

The suggested replacement of vec![0; len] is not a viable replacement because the vector element type is not something that can be "0".

---

clippy 0.0.212 (b2601be 2018-11-27)

[oli-obk]

We should just stop emitting this lint for set_len entirely.

[dtolnay]

I deleted this lint in #3478.