error: Duplicate value
  --> tests/compile-fail/duplicate_value.rs:12:5
   |
12 |     D = 9,
   |     ^

error[E0081]: discriminant value `9` assigned more than once
  --> tests/compile-fail/duplicate_value.rs:7:1
   |
7  | pub(crate) enum EG {
   | ^^^^^^^^^^^^^^^^^^
...
10 |     B = 9,
   |         - `9` assigned here
11 |     C = 2,
12 |     D = 9,
   |         - `9` assigned here