# E0251

A constructor pattern with the wrong number of fields, such as `Some` or `Shape.Square(a, b)`. Spans the pattern.

**Machine-applicable fix:** none.

## Example

This program fails with `E0251`.

```oska
fn count(x: Option<Int>) -> Int {
    match x {
        Some => 1
        None => 0
    }
}
```

## Fixed

The same program, fixed.

```oska
fn count(x: Option<Int>) -> Int {
    match x {
        Some(_) => 1
        None => 0
    }
}
```

Listed in the [checker notes](/checker.md#e0251). `oskac explain E0251` prints this entry offline.