import type { FieldContext } from '../../types.js';
/**
 * Validation rule that makes a field required when a specified condition is met.
 * This rule is implicit, meaning it runs even when the field value is undefined.
 *
 * @param checker - Callback function that returns true if the field should be required
 *
 * @example
 * vine.string().optional().use(requiredWhen((field) => {
 *   return field.data.role === 'admin'
 * }))
 */
export declare const requiredWhen: (options: (field: FieldContext) => boolean) => import("../../types.js").Validation<(field: FieldContext) => boolean>;