/**
 * Which variant of a union a given value currently inhabits. Discriminated
 * unions read the tag property directly; plain unions score each object variant
 * by how many of its required properties the value carries (a best-effort match
 * when Pydantic emitted no discriminator). Returns `-1` when no variant is
 * active (an unset/`null` value, or nothing matches).
 */
import type { UnionVariant } from './field-model';
import type { JsonSchema } from './types';
export declare function activeVariantIndex(value: unknown, variants: readonly UnionVariant[], discriminator: string | undefined, root: JsonSchema): number;
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