# XO0428: two variants of a valued enum have the same value

A valued enum maps each variant to a value, and `E.from(v)` and the JSON decoder go back from the value to the variant, so the values of one enum are unique. A variant without a value takes the previous variant's value plus one for `Int`, so `A = 1, B = 1` and `A = 1, B = 0, C` (C is 1) both repeat a value. See core 2.3.

## Example

```xo
enum Weekday: Int { Mon = 1, Tue = 1 }
```

## Fix

```xo
enum Weekday: Int { Mon = 1, Tue = 2 }
```

Run `xo explain XO0428` for this text in a terminal, or see
[section 10.6 of the specification](../../spec/core/#106-diagnostic-codes).