error[E0308]: mismatched types
  --> $DIR/self-span.rs:17:21
   |
17 |         let _: () = self;
   |                --   ^^^^ expected `()`, found struct `S`
   |                |
   |                expected due to this

error: the `Self` constructor can only be used with tuple or unit structs
  --> $DIR/self-span.rs:18:23
   |
18 |         let _: Self = Self;
   |                       ^^^^ help: use curly brackets: `Self { /* fields */ }`

error[E0308]: mismatched types
  --> $DIR/self-span.rs:25:21
   |
25 |         let _: () = self;
   |                --   ^^^^ expected `()`, found enum `E`
   |                |
   |                expected due to this

error[E0533]: expected unit struct, unit variant or constant, found struct variant `Self::V`
  --> $DIR/self-span.rs:26:23
   |
26 |         let _: Self = Self::V;
   |                       ^^^^^^^