import { type AsymmetricMatcher } from './shared/predicates';
import type { MatcherResult } from './shared/types';
declare global {
    namespace jest {
        interface Matchers<R> {
            toMatchLeft(expected: unknown): R;
        }
    }
}
/**
 * Asserts that the left side of an `Either` matches a value, partial object, or
 * regular expression.
 *
 * @typeParam L Type of the left value contained in the `Either`.
 *
 * @param expected Pattern, partial object, or asymmetric matcher for the left.
 *
 * @example
 * ```typescript
 * import { left } from 'fp-ts/lib/Either'
 *
 * test('passes when left of Either matches an object', () => {
 *   const actual = left({ test: 'ok', foo: 'bar' })
 *   expect(actual).toMatchLeft({ test: 'ok' })
 * })
 *
 * test('passes when left of Either does not match an object', () => {
 *   const actual = left({ test: 'unexpected', foo: 'bar' })
 *   expect(actual).not.toMatchLeft({ test: 'ok' })
 * })
 * ```
 */
export declare function toMatchLeft(actual: unknown, expected: RegExp | AsymmetricMatcher): MatcherResult;
export declare function toMatchLeft<L>(actual: unknown, expected: Partial<L> | AsymmetricMatcher): MatcherResult;