/**
 * Puts `key` into the backing array, if it is not already present. Returns
 * the index of the `key` in the backing array.
 */
export declare let put: (strarr: FastStringArray, key: string) => number;
/**
 * FastStringArray acts like a `Set` (allowing only one occurrence of a string
 * `key`), but provides the index of the `key` in the backing array.
 *
 * This is designed to allow synchronizing a second array with the contents of
 * the backing array, like how `sourcesContent[i]` is the source content
 * associated with `source[i]`, and there are never duplicates.
 */
export declare class FastStringArray {
    indexes: {
        [key: string]: number;
    };
    array: readonly string[];
}