error[E0277]: the type `UnsafeCell` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary --> $DIR/interior-mutability.rs:5:18 | LL | catch_unwind(|| { x.set(23); }); | ------------ ^^^^^^^^^^^^^^^^^ `UnsafeCell` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary | | | required by a bound introduced by this call | = help: within `Cell`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell` note: required because it appears within the type `Cell` --> $SRC_DIR/core/src/cell.rs:LL:COL = note: required for `&Cell` to implement `UnwindSafe` note: required because it's used within this closure --> $DIR/interior-mutability.rs:5:18 | LL | catch_unwind(|| { x.set(23); }); | ^^ note: required by a bound in `catch_unwind` --> $SRC_DIR/std/src/panic.rs:LL:COL error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.