error[E0381]: borrow of possibly-uninitialized variable: `x`
  --> $DIR/borrowck-use-uninitialized-in-cast-trait.rs:9:13
   |
LL |     let y = x as *const dyn Foo;
   |             ^ use of possibly-uninitialized `*x`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0381`.