Jumps and labels

Use break and continue to control loops. Labels can identify an enclosing loop or provide a target for goto.

break and continue

break exits the innermost loop, while, or for. continue skips the remainder of the current iteration and starts the next one.

for value in values {
    if shouldStop(value) {
        break
    }

    if shouldSkip(value) {
        continue
    }

    consume(value)
}

Both transfers are valid as statements and as abrupt expressions. Expression forms are useful in an inline if or match branch and do not contribute a type because execution does not continue through that path.

outer: loop {
    for value in values {
        match classify(value) {
            .Stop => break outer
            .Skip => continue
            .Use => consume(value)
        }
    }
}

Loop-transfer rules

• break and continue must occur inside a loop; otherwise Raven reports RAV2600 and RAV2601, respectively.
• Statement-form transfers cannot be placed directly in expression contexts; doing so reports RAV1902 for break or RAV1903 for continue. Use their expression forms in those positions.
• A labeled transfer must name an enclosing labeled loop. Targeting an ordinary statement label reports RAV2606.

Labels

A label is an identifier followed by : before a statement. Multiple labels may refer to the same statement, and a label followed immediately by a newline is still a valid target.

start:
performWork()

Label names belong to their containing function, lambda, or accessor. A name may be declared only once in that body; duplicates report RAV2500. Escaped identifiers use their logical name for lookup, so @loop: and goto @loop refer to the same label. A label is statement syntax; placing one directly in an expression context reports RAV1905.

goto

goto name transfers execution to a label in the same function-like body. The target may appear before or after the jump.

func retryingWork() {
start:
    let succeeded = tryOnce()
    if not succeeded {
        goto start
    }
}

A jump cannot cross into another function, lambda, or accessor. Any scopes it leaves are unwound before execution continues at the target. An unknown target reports RAV2501; a missing or invalid label name reports RAV2502. goto is a statement and using it directly in an expression context reports RAV1904.