error[E0782]: expected a type, found a trait --> $DIR/ice-unsized-fn-params.rs:13:13 | LL | fn g(b: B) -> B; | ^ | = note: `B` it is dyn-incompatible, so it can't be `dyn` help: use a new generic type parameter, constrained by `B` | LL | 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 | fn g(b: impl B) -> B; | ++++ error[E0782]: expected a type, found a trait --> $DIR/ice-unsized-fn-params.rs:13:19 | LL | fn g(b: B) -> B; | ^ | help: `B` is dyn-incompatible, use `impl B` to return an opaque type, as long as you return a single underlying type | LL | fn g(b: B) -> impl B; | ++++ error[E0782]: expected a type, found a trait --> $DIR/ice-unsized-fn-params.rs:7:13 | LL | fn f(a: A) -> A; | ^ | = note: `A` it is dyn-incompatible, so it can't be `dyn` help: use a new generic type parameter, constrained by `A` | LL | 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 | fn f(a: impl A) -> A; | ++++ error[E0782]: expected a type, found a trait --> $DIR/ice-unsized-fn-params.rs:7:19 | LL | fn f(a: A) -> A; | ^ | help: `A` is dyn-incompatible, use `impl A` to return an opaque type, as long as you return a single underlying type | LL | fn f(a: A) -> impl A; | ++++ error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0782`.