import type { Overflow } from "../../types/index.js";
/**
 * Construct a time interval from a single point plus an ISO 8601 duration, anchored at either end.
 *
 * - `anchor: "start"` treats `value` as the interval start and adds `duration` to get the end.
 * - `anchor: "end"` treats `value` as the interval end and subtracts `duration` to get the start.
 * - `PlainTime` has no calendar, so a `duration` with a nonzero years/months/weeks/days component
 *   cannot be resolved against a bare clock time — there is no `relativeTo` to supply (mirrors
 *   A2/A3's documented `relativeTo` gap). `Temporal.PlainTime.prototype.add` silently discards
 *   those fields rather than throwing, so this is checked explicitly and returns null.
 * - A `duration` that wraps past midnight (e.g. `"23:00:00"` + `"PT2H"`) produces a span PlainTime
 *   can't represent (no date component for the day rollover) and returns null, same as any other
 *   inverted span.
 * - `overflow` ("constrain" (default) | "reject") is accepted for API consistency with sibling
 *   `intervalFromDuration*` functions, but `PlainTime` arithmetic always wraps around the clock
 *   rather than producing an out-of-range value, so it has no observable effect here (mirrors
 *   `addTime`'s own documented no-op).
 * - Returns null on invalid input (unparseable `value`, invalid `duration`, or an `anchor` other
 *   than `"start"`/`"end"`).
 *
 * @param value ISO PlainTime string
 * @param duration ISO 8601 duration string
 * @param anchor "start" | "end" — which endpoint `value` represents
 * @param options optional: overflow ("constrain" | "reject" — accepted but inert, see above)
 * @returns `{ start, end }` with the constructed span, or null on invalid input
 *
 * @example intervalFromDurationTime("12:00:00", "PT1H", "start") // { start: "12:00:00", end: "13:00:00" }
 * @example intervalFromDurationTime("13:00:00", "PT1H", "end") // { start: "12:00:00", end: "13:00:00" }
 * @example intervalFromDurationTime("12:00:00", "P1D", "start") // null (date units need relativeTo, unsupported)
 * @example intervalFromDurationTime("23:00:00", "PT2H", "start") // null (wraps past midnight, inverted span)
 * @example intervalFromDurationTime("invalid", "PT1H", "start") // null
 */
export declare function intervalFromDurationTime(value: string, duration: string, anchor: "start" | "end", options?: {
    overflow?: Overflow;
}): {
    start: string;
    end: string;
} | null;