error[E0271]: type mismatch resolving `impl Trait + ?Sized <: dyn Send`
  --> $DIR/unsized_coercion3.rs:13:17
   |
LL |         let x = hello();
   |                 ^^^^^^^ types differ

error[E0308]: mismatched types
  --> $DIR/unsized_coercion3.rs:18:14
   |
LL | fn hello() -> Box<impl Trait + ?Sized> {
   |                   ------------------- the expected opaque type
...
LL |     Box::new(1u32)
   |     -------- ^^^^ types differ
   |     |
   |     arguments to this function are incorrect
   |
   = note: expected opaque type `impl Trait + ?Sized`
                     found type `u32`
note: associated function defined here
  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL

error[E0277]: the size for values of type `impl Trait + ?Sized` cannot be known at compilation time
  --> $DIR/unsized_coercion3.rs:18:14
   |
LL |     Box::new(1u32)
   |     -------- ^^^^ doesn't have a size known at compile-time
   |     |
   |     required by a bound introduced by this call
   |
   = help: the trait `Sized` is not implemented for `impl Trait + ?Sized`
note: required by a bound in `Box::<T>::new`
  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0271, E0277, E0308.
For more information about an error, try `rustc --explain E0271`.