error[E0392]: type parameter `T` is never used
  --> $DIR/E0374.rs:4:12
   |
LL | struct Foo<T: ?Sized> {
   |            ^ unused type parameter
   |
   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`

error[E0374]: the trait `CoerceUnsized` may only be implemented for a coercion between structures
  --> $DIR/E0374.rs:8:1
   |
LL | / impl<T, U> CoerceUnsized<Foo<U>> for Foo<T>
LL | |     where T: CoerceUnsized<U> {}
   | |_____________________________^
   |
   = note: expected a single field to be coerced, none found

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0374, E0392.
For more information about an error, try `rustc --explain E0374`.