warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/specialization-polarity.rs:5:12
   |
LL | #![feature(specialization)]
   |            ^^^^^^^^^^^^^^
   |
   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
   = help: consider using `min_specialization` instead, which is more stable and complete
   = note: `#[warn(incomplete_features)]` on by default

error[E0751]: found both positive and negative implementation of trait `Foo` for type `u8`:
  --> $DIR/specialization-polarity.rs:10:1
   |
LL | impl<T> Foo for T {}
   | ----------------- positive implementation here
LL | impl !Foo for u8 {}
   | ^^^^^^^^^^^^^^^^ negative implementation here

error[E0751]: found both positive and negative implementation of trait `Bar` for type `u8`:
  --> $DIR/specialization-polarity.rs:15:1
   |
LL | impl<T> !Bar for T {}
   | ------------------ negative implementation here
LL | impl Bar for u8 {}
   | ^^^^^^^^^^^^^^^ positive implementation here

error: aborting due to 2 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0751`.