error[E0081]: discriminant value `2` assigned more than once
 --> tests/failed/07-discriminant.rs:4:1
  |
4 | enum Foo {
  | ^^^^^^^^
5 |     A = 2,
  |         - `2` assigned here
6 |     B = 0,
  |     - discriminant for `D` incremented from this startpoint (`B` + 2 variants later => `D` = 2)
7 |     C,
8 |     D,
  |     - `2` assigned here