error[E0271]: type mismatch resolving `impl Trait <: dyn Trait`
  --> $DIR/unsized_coercion.rs:14:17
   |
LL |         let x = hello();
   |                 ^^^^^^^ types differ

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

error: aborting due to 2 previous errors

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