1 The `issue` value is missing in a stability attribute.
3 Erroneous code example:
6 #![feature(staged_api)]
7 #![stable(since = "1.0.0", feature = "test")]
9 #[unstable(feature = "_unstable_fn")] // invalid
12 #[rustc_const_unstable(feature = "_unstable_const_fn")] // invalid
13 fn _unstable_const_fn() {}
16 To fix this issue, you need to provide the `issue` field. Example:
19 #![feature(staged_api)]
20 #![stable(since = "1.0.0", feature = "test")]
22 #[unstable(feature = "_unstable_fn", issue = "none")] // ok!
25 #[rustc_const_unstable(
26 feature = "_unstable_const_fn",
29 fn _unstable_const_fn() {}
32 See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix
33 of the Book and the [Stability attributes][stability-attributes] section of the
34 Rustc Dev Guide for more details.
36 [how-rust-made-nightly]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html
37 [stability-attributes]: https://rustc-dev-guide.rust-lang.org/stability.html