# T305

> null arm on a value that cannot be null

**Severity** Warning

A `match` has a `null` arm, but the subject's type is not nullable, so the arm can never run. This often happens after a value was already defaulted with `??`.

Remove the `null` arm, or match on the original nullable value instead.

## Failing example

```flowscope
script "OI direction"
data oi = subscribe(data.oi)
on oi.close {
  let change = (oi.close ?? 0.0) - (oi.close[1] ?? 0.0)
  let word = match change {
    null => "unknown"
    v if v > 0.0 => "rising"
    _ => "falling"
  }
  log.debug(word)
}
```

## Fixed example

```flowscope
script "OI direction"
data oi = subscribe(data.oi)
on oi.close {
  let change = oi.close - oi.close[1]
  let word = match change {
    null => "unknown"
    v if v > 0.0 => "rising"
    _ => "falling"
  }
  log.debug(word)
}
```

## Related

- [T304](/docs/scripting/reference/diagnostics/t304)
- [N001](/docs/scripting/reference/diagnostics/n001)