/**
 * Extracts a string result from a stdout/stderr pair.
 * Returns `stdout` on success; rejects with `stderr` if it is non-empty.
 *
 * @param x - An object containing `stdout` and `stderr` strings
 * @returns A promise resolving to `stdout`, or rejecting with `stderr`
 */
export declare function stringFromStdErrOut(x: {
    stdout: string;
    stderr: string;
}): Promise<string>;