Rust errors / Attributes, macros and features
Rust compiler error · checked with rustc 1.99.0
Rust error E0549: deprecated attribute must be paired with either stable or unstable attribute
What it meansA deprecated attribute wasn't paired with a stable/unstable attribute with #![feature(staged_api)] enabled.
What rustc prints
error[E0549]: deprecated attribute must be paired with either stable or unstable attribute
--> main.rs:5:1
|
5 | / #[deprecated(
6 | | since = "1.0.1",
7 | | note = "explanation for deprecation"
8 | | )] // invalid
| |__^Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
The compiler team's explanation
A deprecated attribute wasn't paired with a stable/unstable attribute with #![feature(staged_api)] enabled.
Erroneous code example:
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "test")]
#[deprecated(
since = "1.0.1",
note = "explanation for deprecation"
)] // invalid
fn _deprecated_fn() {}To fix this issue, you need to add also an attribute stable or unstable. Example:
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "test")]
#[stable(since = "1.0.0", feature = "test")]
#[deprecated(
since = "1.0.1",
note = "explanation for deprecation"
)] // ok!
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.
From rustc --explain E0549 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
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