import { Expression } from "../core/signals.js";
/**w
 * Map expression values to strings except `null` or `undefined`.
 *
 * See {@link map}.
 *
 * @example
 * ```tsx
 * import { optionalString } from "rvx";
 *
 * <div some-value={optionalString(false)} />; // <div some-value="false" />
 * <div some-value={optionalString(null)} />; // <div />
 * <div some-value={optionalString(undefined)} />; // <div />
 * ```
 */
export declare function optionalString<T>(input: Expression<T>): Expression<string | Exclude<T, Exclude<T, null | undefined>>>;