error[E0658]: attributes on expressions are experimental --> $DIR/feature-gate-stmt_expr_attributes.rs:1:16 | LL | const X: i32 = #[allow(dead_code)] 8; | ^^^^^^^^^^^^^^^^^^^ | = note: see issue #15701 for more information = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.