warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/equality.rs:1:12
   |
LL | #![feature(specialization)]
   |            ^^^^^^^^^^^^^^
   |
   = note: `#[warn(incomplete_features)]` on by default
   = 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

error[E0308]: mismatched types
  --> $DIR/equality.rs:15:5
   |
LL | fn two(x: bool) -> impl Foo {
   |                    -------- expected because this return type...
LL |     if x {
LL |         return 1_i32;
   |                ----- ...is found to be `i32` here
LL |     }
LL |     0_u32
   |     ^^^^^ expected `i32`, found `u32`
   |
   = note: to return `impl Trait`, all returned values must be of the same type
   = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
   = help: if the trait `Foo` were object safe, you could return a boxed trait object
   = note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
   = help: you could instead create a new `enum` with a variant for each returned type

error[E0277]: cannot add `impl Foo` to `u32`
  --> $DIR/equality.rs:24:11
   |
LL |         n + sum_to(n - 1)
   |           ^ no implementation for `u32 + impl Foo`
   |
   = help: the trait `Add<impl Foo>` is not implemented for `u32`

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

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.