warning: box pattern syntax is experimental
  --> $DIR/cfg-false-feature.rs:16:9
   |
LL |     let box _ = Box::new(0);
   |         ^^^^^
   |
   = note: see issue #29641 <https://github.com/rust-lang/rust/issues/29641> for more information
   = help: add `#![feature(box_patterns)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = warning: unstable syntax can change at any point in the future, causing a hard error!
   = note: for more information, see issue #65860 <https://github.com/rust-lang/rust/issues/65860>

warning: trait aliases are experimental
  --> $DIR/cfg-false-feature.rs:12:1
   |
LL | trait A = Clone;
   | ^^^^^^^^^^^^^^^^
   |
   = note: see issue #41517 <https://github.com/rust-lang/rust/issues/41517> for more information
   = help: add `#![feature(trait_alias)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = warning: unstable syntax can change at any point in the future, causing a hard error!
   = note: for more information, see issue #65860 <https://github.com/rust-lang/rust/issues/65860>

warning: 2 warnings emitted