/**
 * Represents source text that can be missing.
 */
export declare type NullableSourceText = string | null;
export interface SourceStore {
    /**
     * Registers a `url`, optionally with its source text.
     *
     * @param url URL of the source text.
     * @param sourceText Source text corresponding to the provided URL, or `null`.
     * @returns Boolean indicating if the source store was updated.
     */
    set(url: string, sourceText: NullableSourceText): boolean;
    /**
     * Returns the current source text for the provided `url`.
     *
     * - If the `url` is unknown, returns `undefined`.
     * - If the `url` is known but does not have any associated source text,
     *   returns `null`.
     * - If the `url` is known and the store has its source text, returns the
     *   source text (a `string`).
     *
     * @param url URL of the source text.
     */
    get(url: string): NullableSourceText | undefined;
    [Symbol.iterator](): Iterator<[string, NullableSourceText]>;
}
/**
 * This is basically a `Map` with a setter checking for changes instead
 * of returning `this`.
 */
export declare class MemorySourceStore implements SourceStore {
    private readonly urlToSourceText;
    constructor(initialData?: Iterable<[string, NullableSourceText]>);
    /**
     * Registers a `url`, optionally with its source text.
     *
     * Throws an error if the URL is already set and the value differs.
     *
     * @param url URL to set.
     * @param sourceText Source text corresponding to the provided URL.
     * @returns Boolean indicating if the source store was updated.
     */
    set(url: string, sourceText: NullableSourceText): boolean;
    get(url: string): NullableSourceText | undefined;
    [Symbol.iterator](): Iterator<[string, NullableSourceText]>;
}