error[E0308]: mismatched types
  --> $DIR/mir-unpretty.rs:4:17
   |
LL |     let x: () = 0;
   |                 ^ expected (), found integer
   |
   = note: expected type `()`
              found type `{integer}`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.