import { HasTag, InferKind, SomeSpec, Spec, SpecsTags, SpecSuccess, SpectypesError } from './types.js';
/**
 * Creates a union validator spec.
 *
 * @param specs Specs to validate union cases
 */
export declare const union: <Specs extends readonly Spec[] = readonly SomeSpec[]>(...specs: Specs & {
    readonly [Index in keyof Specs]: Specs[Index] extends Spec ? HasTag<Specs[Index], 'optional'> extends true ? SpectypesError<'optional', 'union'> : HasTag<Specs[Index], 'filter'> extends true ? SpectypesError<'filter', 'union'> : HasTag<Specs[Index], 'unknown'> extends true ? SpectypesError<'unknown', 'union'> : HasTag<Specs[Index], 'union'> extends true ? SpectypesError<'union', 'union'> : HasTag<Specs[Index], 'lazy'> extends true ? SpectypesError<'lazy', 'union'> : Specs[Index] : never;
}) => Spec<[
    'union',
    ...SpecsTags<Specs>
], InferKind<Specs>, {
    readonly [Index in keyof Specs]: Specs[Index] extends Spec ? SpecSuccess<Specs[Index]> : never;
}[number]>;