# XO0917: a catch-all variant built from a run time value

A valued enum's catch-all keeps the values no variant names. Built directly from a run time value, it holds whatever the value is, even one a named variant has, and then compares unequal to that variant. `E.from(v)` returns the named variant for a known value and the catch-all otherwise. Keep the direct form with `// xo:allow XO0917 REASON` when the value is known to be new. See core 2.3 and decision 0493.

## Example

```xo
fn class_of(s: Str) -> StorageClass { StorageClass.Unknown(s) }
```

## Fix

```xo
fn class_of(s: Str) -> StorageClass { StorageClass.from(s) }
```

Run `xo explain XO0917` for this text in a terminal, or see
[section 10.6 of the specification](../../spec/core/#106-diagnostic-codes).