Multiple stability attributes were declared on the same item.
Erroneous code example:
#![allow(unused)]
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "rust1")]
fn main() {
#[stable(feature = "rust1", since = "1.0.0")]
#[stable(feature = "test", since = "2.0.0")]
fn foo() {}
}
ⓘ
To fix this issue, ensure that each item has at most one stability attribute.
#![allow(unused)]
#![feature(staged_api)]
#![allow(internal_features)]
#![stable(since = "1.0.0", feature = "rust1")]
fn main() {
#[stable(feature = "test", since = "2.0.0")]
fn foo() {}
}
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.