Match combinations with tuple patterns

Match a tuple when the answer depends on several values together. Each component takes a pattern, and the cases cover combinations of components:

def combine(left: Option[i64], right: Option[i64]) -> Result[i64, OverflowError[i64]]:
    match (left, right):
        case (Some(a), Some(b)):
            Ok(a + b)
        case (Some(a), Nothing):
            Ok(a)
        case (Nothing, Some(b)):
            Ok(b)
        case (Nothing, Nothing):
            Ok(0)

def main() -> Result[(), IoError | OverflowError[i64]]:
    print(combine(Some(3), Some(4))?)?
    print(combine(Nothing, Some(5))?)?
    Ok(())

7
5

Leaving out (Nothing, Nothing) is an error: both inputs can be absent. Tuple patterns also nest inside enum payloads, such as Some((value, offset)). Write (pattern,) for a singleton tuple; (pattern) groups a pattern.

Matching an owned tuple transfers owned components into the case’s bindings and destroys ignored components. Match &value or &mut value to borrow its components, as in borrowed matching. The matching reference describes coverage and pattern limits.