`#[track_caller]` does not work on `fn drop`

[SludgePhD]

Putting #[track_caller] on a fn drop implementation does not attribute the panic to the code that drops the value. Instead, some location in the standard library is blamed:

struct S;

impl Drop for S {
    #[track_caller]
    fn drop(&mut self) {
        panic!("panicking!");
    }
}

fn main() {
    let _variable = S;
}

Outputs:

thread 'main' panicked at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/ptr/mod.rs:497:1:
panicking!

[bjorn3]

Dropping a value will call core::ptr::drop_in_place (also called the drop glue) which then calls the drop function of the type followed by drop_in_place for all fields. As drop_in_place doesn't have #[track_caller], attaching #[track_caller] to Drop::drop will blame drop_in_place. Adding #[track_caller] to drop_in_place (+ compiler changes to correctly create the drop glue and to invoke the drop glue with the extra &'static Location argument) should solve this, but I did expect it to cause a non-trivial perf regression.