1 error[E0038]: the trait `Foo` cannot be made into an object
2 --> $DIR/issue-38604.rs:24:13
4 LL | let _f: Box<Foo> = //~ ERROR `Foo` cannot be made into an object
5 | ^^^^^^^^ the trait `Foo` cannot be made into an object
7 = note: the trait cannot use `Self` as a type parameter in the supertraits or where-clauses
9 error[E0038]: the trait `Foo` cannot be made into an object
10 --> $DIR/issue-38604.rs:25:9
12 LL | Box::new(()); //~ ERROR `Foo` cannot be made into an object
13 | ^^^^^^^^^^^^ the trait `Foo` cannot be made into an object
15 = note: the trait cannot use `Self` as a type parameter in the supertraits or where-clauses
16 = note: required because of the requirements on the impl of `std::ops::CoerceUnsized<std::boxed::Box<dyn Foo>>` for `std::boxed::Box<()>`
18 error: aborting due to 2 previous errors
20 For more information about this error, try `rustc --explain E0038`.