error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> $DIR/defaults-wf.rs:7:15
   |
LL |     type Ty = Vec<[u8]>;
   |               ^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `[u8]`
note: required by a bound in `Vec`
  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
   |
LL | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
   |                ^ required by this bound in `Vec`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.