error[E0658]: the `#[no_core]` attribute is an experimental feature --> $DIR/cfg-attr-multi-invalid-2.rs:4:29 | LL | #![cfg_attr(broken, no_std, no_core)] | ^^^^^^^ | = note: see issue #29639 for more information = help: add `#![feature(no_core)]` to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.