error[E0277]: the size for values of type `X` cannot be known at compilation time
  --> $DIR/unsized7.rs:12:21
   |
LL | impl<X: ?Sized + T> T1<X> for S3<X> {
   |      -              ^^^^^ doesn't have a size known at compile-time
   |      |
   |      this type parameter needs to be `Sized`
   |
note: required by an implicit `Sized` bound in `T1`
  --> $DIR/unsized7.rs:7:10
   |
LL | trait T1<Z: T> {
   |          ^ required by the implicit `Sized` requirement on this type parameter in `T1`
help: consider removing the `?Sized` bound to make the type parameter `Sized`
   |
LL - impl<X: ?Sized + T> T1<X> for S3<X> {
LL + impl<X: T> T1<X> for S3<X> {
   |
help: consider relaxing the implicit `Sized` restriction
   |
LL | trait T1<Z: T + ?Sized> {
   |               ++++++++

error[E0046]: not all trait items implemented, missing: `dummy`
  --> $DIR/unsized7.rs:12:1
   |
LL |     fn dummy(&self) -> Z;
   |     --------------------- `dummy` from trait
...
LL | impl<X: ?Sized + T> T1<X> for S3<X> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `dummy` in implementation

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0046, E0277.
For more information about an error, try `rustc --explain E0046`.