error[E0277]: the size for values of type `X` cannot be known at compilation time
--> $DIR/unsized-trait-impl-trait-arg.rs:8:17
|
+LL | trait T2<Z> {
+ | - required by this bound in `T2`
+...
LL | impl<X: ?Sized> T2<X> for S4<X> {
| - ^^^^^ doesn't have a size known at compile-time
| |