error[E0658]: use of unstable library feature 'allocator_api' --> $DIR/alloc-unstable-fail.rs:4:26 | LL | let _boxed: Box = Box::new(10); | ^ | = note: see issue #32838 for more information = help: add `#![feature(allocator_api)]` to the crate attributes to enable error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.