error[E0782]: trait objects must include the `dyn` keyword --> $DIR/dyn-2021-edition-error.rs:3:17 | LL | fn function(x: &SomeTrait, y: Box) { | ^^^^^^^^^ | help: use a new generic type parameter, constrained by `SomeTrait` | LL | fn function(x: &T, y: Box) { | ++++++++++++++ ~ help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | LL | fn function(x: &impl SomeTrait, y: Box) { | ++++ help: alternatively, use a trait object to accept any type that implements `SomeTrait`, accessing its methods at runtime using dynamic dispatch | LL | fn function(x: &dyn SomeTrait, y: Box) { | +++ error[E0782]: trait objects must include the `dyn` keyword --> $DIR/dyn-2021-edition-error.rs:3:35 | LL | fn function(x: &SomeTrait, y: Box) { | ^^^^^^^^^ | help: add `dyn` keyword before this trait | LL | fn function(x: &SomeTrait, y: Box) { | +++ error[E0782]: trait objects must include the `dyn` keyword --> $DIR/dyn-2021-edition-error.rs:6:14 | LL | let _x: &SomeTrait = todo!(); | ^^^^^^^^^ | help: add `dyn` keyword before this trait | LL | let _x: &dyn SomeTrait = todo!(); | +++ error: aborting due to 3 previous errors For more information about this error, try `rustc --explain E0782`.