Function checkDeadline

src/common/interruptible.ts:27–34

(deadline: number | undefined)

 * frame is immutable: entering a span creates a new frame; exiting restores
 * the saved previous frame object.
 *
 *  - `at`: absolute ms timestamp beyond which execution should not proceed.
 *  - `owner`: label of the span whose deadline is the EFFECTIVE one (i.e. the
 *    span that owns `at`). `undefined` for an unlabelled span.
 *  - `spans`: labels of all active spans, outermost first. Unlabelled spans
 *    contribute nothing.
 */
export interface DeadlineFrame {
  at: number;
  owner?: string;
  spans: string[];