A builtin-macro was defined more than once.
Erroneous code example:
#![feature(decl_macro)]
#![feature(rustc_attrs)]
#[rustc_builtin_macro]
pub macro test($item:item) {
/* compiler built-in */
}
mod inner {
#[rustc_builtin_macro]
pub macro test($item:item) {
/* compiler built-in */
}
}
RunTo fix the issue, remove the duplicate declaration:
#![feature(decl_macro)]
#![feature(rustc_attrs)]
#[rustc_builtin_macro]
pub macro test($item:item) {
/* compiler built-in */
}
RunIn very rare edge cases, this may happen when loading core
or std
twice,
once with check
metadata and once with build
metadata.
For more information, see #75176.