error[E0658]: attributes on expressions are experimental --> $DIR/stmt-expr-gated.rs:2:13 | LL | let _ = #[deny(warnings)] if true { | ^^^^^^^^^^^^^^^^^ | = note: see issue #15701 for more information = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.