error: non-binding let on a type that implements `Drop`
  --> $DIR/ice-4968.rs:16:9
   |
LL |         let _: Vec<ManuallyDrop<T::Assoc>> = mem::transmute(slice);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[deny(clippy::let_underscore_drop)]` on by default
   = help: consider using an underscore-prefixed named binding or dropping explicitly with `std::mem::drop`

error: aborting due to previous error