 --> [ local path prefix ]/enums/duplicate_value.fpp:3:17
  |
3 | enum E { X = a, Y = b + 1 }
  |                 ^^^^^^^^^ duplicate enum constant `2`
  |
 ::: [ local path prefix ]/enums/duplicate_value.fpp:3:10
  |
3 | enum E { X = a, Y = b + 1 }
  |          ----- previously defined here

