warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:9:19 | LL | trait A { fn g(b: B) -> B; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see = note: `B` it is not object safe, so it can't be `dyn` = note: `#[warn(bare_trait_objects)]` on by default help: use a new generic type parameter, constrained by `B` | LL | trait A { fn g(b: T) -> B; } | ++++++ ~ 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 | trait A { fn g(b: impl B) -> B; } | ++++ warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:9:25 | LL | trait A { fn g(b: B) -> B; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see help: `B` is not object safe, use `impl B` to return an opaque type, as long as you return a single underlying type | LL | trait A { fn g(b: B) -> impl B; } | ++++ warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:1:19 | LL | trait B { fn f(a: A) -> A; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see = note: `A` it is not object safe, so it can't be `dyn` help: use a new generic type parameter, constrained by `A` | LL | trait B { fn f(a: T) -> A; } | ++++++ ~ 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 | trait B { fn f(a: impl A) -> A; } | ++++ warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:1:25 | LL | trait B { fn f(a: A) -> A; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see help: `A` is not object safe, use `impl A` to return an opaque type, as long as you return a single underlying type | LL | trait B { fn f(a: A) -> impl A; } | ++++ warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:1:19 | LL | trait B { fn f(a: A) -> A; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see = note: `A` it is not object safe, so it can't be `dyn` = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` help: use a new generic type parameter, constrained by `A` | LL | trait B { fn f(a: T) -> A; } | ++++++ ~ 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 | trait B { fn f(a: impl A) -> A; } | ++++ error[E0038]: the trait `A` cannot be made into an object --> $DIR/avoid-ice-on-warning-3.rs:1:19 | LL | trait B { fn f(a: A) -> A; } | ^ `A` 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 --> $DIR/avoid-ice-on-warning-3.rs:9:14 | LL | trait A { fn g(b: B) -> B; } | - ^ ...because associated function `g` has no `self` parameter | | | this trait cannot be made into an object... help: consider turning `g` into a method by giving it a `&self` argument | LL | trait A { fn g(&self, b: B) -> B; } | ++++++ help: alternatively, consider constraining `g` so it does not apply to trait objects | LL | trait A { fn g(b: B) -> B where Self: Sized; } | +++++++++++++++++ warning: trait objects without an explicit `dyn` are deprecated --> $DIR/avoid-ice-on-warning-3.rs:9:19 | LL | trait A { fn g(b: B) -> B; } | ^ | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! = note: for more information, see = note: `B` it is not object safe, so it can't be `dyn` = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` help: use a new generic type parameter, constrained by `B` | LL | trait A { fn g(b: T) -> B; } | ++++++ ~ 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 | trait A { fn g(b: impl B) -> B; } | ++++ error[E0038]: the trait `B` cannot be made into an object --> $DIR/avoid-ice-on-warning-3.rs:9:19 | LL | trait A { fn g(b: B) -> B; } | ^ `B` 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 --> $DIR/avoid-ice-on-warning-3.rs:1:14 | LL | trait B { fn f(a: A) -> A; } | - ^ ...because associated function `f` has no `self` parameter | | | this trait cannot be made into an object... help: consider turning `f` into a method by giving it a `&self` argument | LL | trait B { fn f(&self, a: A) -> A; } | ++++++ help: alternatively, consider constraining `f` so it does not apply to trait objects | LL | trait B { fn f(a: A) -> A where Self: Sized; } | +++++++++++++++++ error: aborting due to 2 previous errors; 6 warnings emitted For more information about this error, try `rustc --explain E0038`.