Unused trait methods should create a compile-time warning.

[cedws]

Take this example code.

trait MyThing {
    fn do_stuff(&self) -> bool;
    fn do_other_stuff(&self) -> bool;
}

struct Other {}

impl MyThing for Other {
    fn do_stuff(&self) -> bool {
        true
    }

    fn do_other_stuff(&self) -> bool {
        true
    }
}

fn main() {
    let thing = Other {};

    thing.do_stuff();

    // NOTE: We never call `do_other_stuff`.
}

Even though we never call do_other_stuff, the compiler does not generate a warning that this trait method is unused. We've defined an implementation for it, but this doesn't mean that the method is used.

Apologies if this issue has already been raised.

[steveklabnik]

triage: no change

[SebastianJL]

Just ran into the same thing. Just curious there any plan to implement this?

[mu001999]

#118257 fixed this. We can get the output (play):

warning: method `do_other_stuff` is never used
 --> src/main.rs:3:8
  |
1 | trait MyThing {
  |       ------- method in this trait
2 |     fn do_stuff(&self) -> bool;
3 |     fn do_other_stuff(&self) -> bool;
  |        ^^^^^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: `playground` (bin "playground") generated 1 warning

This can be closed. @steveklabnik