/**
 * Check if a condition is true, or throw an error with custom message.
 * @example
 * ```ts
 *  const a: unknown = 'abc';
 *  // a.length; // expect a compiler error
 *
 *  assertTrue(typeof a === 'string');
 *  a.length; // OK, a is string
 * ```
 *
 * @param condition - The condition to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare function assertTrue(condition: boolean, message?: string, props?: object): asserts condition;
/**
 * Check if a value is neither `null` nor `undefined`.
 * @example
 * ```ts
 *  const a = [1, undefined, 2];   // a is (number | undefined)[]
 *  const b = a.filter(isNonNull); // b is number[]
 * ```
 *
 * @param value - The value to be checked
 * @returns false if the value is `null` or `undefined`, or true otherwise
 */
export declare function isNonNull<T>(value: T): value is NonNullable<T>;
/**
 * Check if a value is neither `null` nor `undefined`, or throw an error with custom message.
 * @example
 * ```ts
 *  function f(v?: string) {
 *    //v.length; // expect a compiler error
 *    assertIsNonNull(v);
 *    v.length; // OK, v is string
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare function assertNonNull<T>(value: T, message?: string, props?: object): asserts value is NonNullable<T>;
/**
 * Check if a value is number.
 * @example
 * ```ts
 *  const a = ['1', 2, '3', 4];   // a is (string | number)[]
 *  const b = a.filter(isNumber); // b is [2, 4], i.e. number[]
 * ```
 *
 * @param value - The value to be checked
 * @returns true if the value is number, or false otherwise
 */
export declare const isNumber: (value: any) => value is number;
/**
 * Check if a value is string.
 * @example
 * ```ts
 *  const a = ['1', 2, '3', 4];   // a is (string | number)[]
 *  const b = a.filter(isString); // b is ['1', '3'], i.e. string[]
 * ```
 *
 * @param value - The value to be checked
 * @returns true if the value is string, or false otherwise
 */
export declare const isString: (value: any) => value is string;
/**
 * Check if a value is boolean.
 * @example
 * ```ts
 *  const a = ['1', true, '3', false]; // a is (string | boolean)[]
 *  const b = a.filter(isBoolean);      // b is [true, false], i.e. boolean[]
 * ```
 *
 * @param value - The value to be checked
 * @returns true if the value is boolean, or false otherwise
 */
export declare const isBoolean: (value: any) => value is boolean;
/**
 * Check if a value is bigint.
 * @example
 * ```ts
 *  const a = [1, BigInt(2), 3, BigInt(4)]; // a is (number | bigint)[]
 *  const b = a.filter(isBigint);           // b is [BigInt(2), BigInt(3)], i.e. bigint[]
 * ```
 *
 * @param value - The value to be checked
 * @returns true if the value is bigint, or false otherwise
 */
export declare const isBigint: (value: any) => value is bigint;
/**
 * Check if a value is an object.
 * @param v - The value to be checked
 * @returns true if the value is an object, or false otherwise
 */
export declare function isObject(v: any): boolean;
/**
 * Returns a function to check if a value is instance of a class.
 * @example
 * ```ts
 *  class A {};
 *  class B {};
 *  const a = [new A(), 1, new B()]; // a is (number | A | B)[]
 *  const b = a.filter(isClass(A));  // b is [new A()], i.e. A[]
 * ```
 *
 * @param Class - The constructor of a class
 * @returns A function
 */
export declare function isClass<T extends {
    new (...args: any[]): unknown;
}>(Class: T): (value: any) => value is InstanceType<T>;
declare const _assertIsNumber: (value: any, message?: string, props?: object) => asserts value is number;
declare const _assertIsString: (value: any, message?: string, props?: object) => asserts value is string;
declare const _assertIsBoolean: (value: any, message?: string, props?: object) => asserts value is boolean;
declare const _assertIsBigint: (value: any, message?: string, props?: object) => asserts value is bigint;
/**
 * Check if a value is number, or throw an error with custom message.
 * @example
 * ```ts
 *  function f(v: boolean | number) {
 *    //v + 1; // expect a compiler error
 *    assertIsNumber(v);
 *    v + 1; // OK, v is number
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare const assertIsNumber: typeof _assertIsNumber;
/**
 * Check if a value is string, or throw an error with custom message.
 * @example
 * ```ts
 *  function f(v: boolean | string) {
 *    //v.length; // expect a compiler error
 *    assertIsString(v);
 *    v.length; // OK, v is string
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare const assertIsString: typeof _assertIsString;
/**
 * Check if a value is boolean, or throw an error with custom message.
 * @example
 * ```ts
 *  function f(v: A) {}
 *
 *  function g(v: boolean | string) {
 *    // f(v); // expect a compiler error
 *    assertIsBoolean(v);
 *    f(v); // OK, v is boolean
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare const assertIsBoolean: typeof _assertIsBoolean;
/**
 * Check if a value is bigint, or throw an error with custom message.
 * @example
 * ```ts
 *  function f(v: bigint) {}
 *
 *  function g(v: bigint | string) {
 *    // f(v); // expect a compiler error
 *    assertIsBigint(v);
 *    f(v); // OK, v is bigint
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare const assertIsBigint: typeof _assertIsBigint;
/**
 * Check if a value is an object, or throw an error with custom message.
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare function assertIsObject(value: any, message?: string, props?: object): void;
/**
 * Check if a value is instance of a class, or throw an error with custom message.
 * @example
 * ```ts
 *  class A {
 *    a() {}
 *  }
 *
 *  function f(v: A | string) {
 *    // v.a(); // expect a compiler error
 *    assertIsClass(A, v);
 *    v.a(); // OK, v is class A
 *  }
 * ```
 *
 * @param value - The value to be checked
 * @param message - Error message, or absent for default message
 * @param props - Extra properties to be added to error message
 */
export declare function assertIsClass<T extends {
    new (...args: any[]): unknown;
}>(Class: T, value: any, message?: string, props?: object): asserts value is InstanceType<T>;
export {};