1 A builtin-macro was defined more than once.
3 Erroneous code example:
6 #![feature(decl_macro)]
7 #![feature(rustc_attrs)]
10 pub macro test($item:item) {
11 /* compiler built-in */
15 #[rustc_builtin_macro]
16 pub macro test($item:item) {
17 /* compiler built-in */
22 To fix the issue, remove the duplicate declaration:
25 #![feature(decl_macro)]
26 #![feature(rustc_attrs)]
28 #[rustc_builtin_macro]
29 pub macro test($item:item) {
30 /* compiler built-in */
34 In very rare edge cases, this may happen when loading `core` or `std` twice,
35 once with `check` metadata and once with `build` metadata.
36 For more information, see [#75176].
38 [#75176]: https://github.com/rust-lang/rust/pull/75176#issuecomment-683234468