1 error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
2 --> $DIR/feature-gate-concat_idents.rs:5:13
4 LL | let a = concat_idents!(X, Y_1);
7 = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
8 = help: add `#![feature(concat_idents)]` to the crate attributes to enable
10 error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
11 --> $DIR/feature-gate-concat_idents.rs:6:13
13 LL | let b = concat_idents!(X, Y_2);
16 = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
17 = help: add `#![feature(concat_idents)]` to the crate attributes to enable
19 error: aborting due to 2 previous errors
21 For more information about this error, try `rustc --explain E0658`.