import { Key, ObjectType, Type, UnionType, ValidationError, ValidationFn } from './types';
export declare const flatten: <T>(arr: T[][]) => T[];
export declare const isPlainObject: (o: unknown) => o is object;
export declare const isObjectType: (o: Type) => o is ObjectType;
export declare const isUnionType: (o: Type) => o is UnionType;
export declare const error: (key: Key, message: string) => ValidationError;
export declare const expected: (key: Key, what: string) => ValidationError;
export declare const oneOf: (key: Key, validationFns: ValidationFn[]) => ValidationFn;
export declare const allOf: (validationFns: ValidationFn[]) => ValidationFn;
export declare const getKeys: <T extends object>(o: T) => (keyof T)[];
export declare const noExtraKeys: (baseKey: Key, keys: string[]) => ValidationFn;
export declare const valueIs: (key: Key, expectedValue: unknown, name: string) => ValidationFn;