# `type.match_unknown_binding`

Pattern names data a case does not carry.

Area 3, [Logic](../topics/logic.md); not declinable; the next step is usually the agent's.

Brackets after a case name the data it carries, and a plain variant carries none:


```jadpo
function describe(outcome: PaymentOutcome) -> Label {
    return match outcome {
        PaymentOutcome.pending(waiting) -> "Pending"
        PaymentOutcome.paid -> "Paid"
    }
}
```

```text
error: `PaymentOutcome.pending` carries no data to name
 --> main.jadpo:3:31
  |
3 |         PaymentOutcome.pending(waiting) -> "Pending"
  |                               ^^^^^^^^^ no data
  reason: `PaymentOutcome.pending` is a plain variant; brackets after a case name the data it carries, and this one carries none.
  next: Write `PaymentOutcome.pending` without brackets (agent)
  rule: type.match_unknown_binding
  help: https://jadpo.dev/docs/errors/type.match_unknown_binding

check failed: 1 error, 2 files
```