export declare class DefaultMap<K, V> {
    private readonly getDefault;
    _map: Map<K, V>;
    constructor(getDefault: () => V);
    get(key: K): V;
}
export declare function extend<T>(a: T[], b: readonly T[]): void;
export declare function astNode<T>(item: {
    astNode?: T | undefined | null;
}): T;
/**
 * A branded type representing a unique identifier for TypeScript nodes.
 * Used to track data about nodes in lookup data structures.
 */
export type TsIdentifier = number & {
    readonly __brand: "TsIdentifier";
};
export declare function uniqueId(): TsIdentifier;
export declare function invariant(condition: unknown, message: string): asserts condition;
export declare function nullThrows<T>(value: T | null | undefined): T;
export declare function isNonNull<T>(value: T | null | undefined): value is T;
export declare function levenshteinDistance(s: string, t: string): number;
export declare function bestMatch<T>(arr: readonly T[], scoreFn: (item: T) => number): T;