error: trait objects without an explicit `dyn` are deprecated --> $DIR/bare-trait-dont-suggest-dyn.rs:6:33 | LL | fn ord_prefer_dot(s: String) -> Ord { | ^^^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see note: the lint level is defined here --> $DIR/bare-trait-dont-suggest-dyn.rs:5:9 | LL | #![deny(bare_trait_objects)] | ^^^^^^^^^^^^^^^^^^ help: if this is an object-safe trait, use `dyn` | LL | fn ord_prefer_dot(s: String) -> dyn Ord { | +++ error[E0038]: the trait `Ord` cannot be made into an object --> $DIR/bare-trait-dont-suggest-dyn.rs:6:33 | LL | fn ord_prefer_dot(s: String) -> Ord { | ^^^ `Ord` cannot be made into an object | note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit --> $SRC_DIR/core/src/cmp.rs:LL:COL | = note: the trait cannot be made into an object because it uses `Self` as a type parameter ::: $SRC_DIR/core/src/cmp.rs:LL:COL | = note: the trait cannot be made into an object because it uses `Self` as a type parameter help: consider using an opaque type instead | LL | fn ord_prefer_dot(s: String) -> impl Ord { | ++++ error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0038`.