warning[E0365]: extern crate `core` is private and cannot be re-exported
  --> $DIR/ice-free.rs:5:9
   |
LL | pub use core as reexported_core;
   |         ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #127909 <https://github.com/rust-lang/rust/issues/127909>
   = note: requested on the command line with `--force-warn pub-use-of-private-extern-crate`
help: consider making the `extern crate` item publicly accessible
   |
LL | pub extern crate core;
   | +++

warning: 1 warning emitted

For more information about this error, try `rustc --explain E0365`.
Future incompatibility report: Future breakage diagnostic:
warning[E0365]: extern crate `core` is private and cannot be re-exported
  --> $DIR/ice-free.rs:5:9
   |
LL | pub use core as reexported_core;
   |         ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #127909 <https://github.com/rust-lang/rust/issues/127909>
   = note: requested on the command line with `--force-warn pub-use-of-private-extern-crate`
help: consider making the `extern crate` item publicly accessible
   |
LL | pub extern crate core;
   | +++