error[E0658]: the `#[default_lib_allocator]` attribute is an experimental feature --> $DIR/feature-gate-allocator_internals.rs:1:1 | LL | #![default_lib_allocator] | ^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: add `#![feature(allocator_internals)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.