The note
value is missing in a stability attribute.
Erroneous code example:
#![allow(unused)]
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "test")]
fn main() {
#[stable(since = "0.1.0", feature = "_deprecated_fn")]
#[deprecated(
since = "1.0.0"
)]
fn _deprecated_fn() {}
}
ⓘ
To fix this issue, you need to provide the note
field. Example:
#![allow(unused)]
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "test")]
fn main() {
#[stable(since = "0.1.0", feature = "_deprecated_fn")]
#[deprecated(
since = "1.0.0",
note = "explanation for deprecation"
)]
fn _deprecated_fn() {}
}
See the How Rust is Made and “Nightly Rust” appendix
of the Book and the Stability attributes section of the
Rustc Dev Guide for more details.