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import { getOrInit } from "../util/state.ts"
export interface Guard<T, Y extends T> {  (value: T): value is Y}
export function is(guard: undefined): Guard<unknown, undefined>export function is(guard: null): Guard<unknown, null>export function is(guard: typeof Number): Guard<unknown, number>export function is(guard: typeof String): Guard<unknown, string>export function is(guard: typeof Boolean): Guard<unknown, boolean>export function is(guard: typeof BigInt): Guard<unknown, bigint>export function is(guard: typeof Symbol): Guard<unknown, symbol>export function is(guard: true): Guard<unknown, true>export function is(guard: false): Guard<unknown, false>export function is<T>(guard: abstract new(...args: any) => T): Guard<unknown, T>export function is<  T extends string | { type: string },  U extends T extends { type: string } ? T["type"] : T,>(  guard: U,): Guard<T, Extract<T, U | { type: U }>>export function is(guard: any): Guard<unknown, any> {  switch (guard) {    case undefined:      return isUndefined    case null:      return isNull    case Number:      return isNumber    case String:      return isString    case Boolean:      return isBoolean    case BigInt:      return isBigInt    case Symbol:      return isSymbol    default:      if (typeof guard === "string") {        return isType(guard)      } else if (typeof guard === "boolean") {        return guard ? isTrue : isFalse      }      {        return isInstance(guard)      }  }}
function isUndefined(x: unknown): x is undefined {  return typeof x === "undefined"}
function isNull(x: unknown): x is null {  return x === null}
function isNumber(x: unknown): x is number {  return typeof x === "number"}
function isString(x: unknown): x is string {  return typeof x === "string"}
function isBoolean(x: unknown): x is boolean {  return typeof x === "boolean"}
function isBigInt(x: unknown): x is bigint {  return typeof x === "bigint"}
function isSymbol(x: unknown): x is symbol {  return typeof x === "symbol"}
function isTrue(x: unknown): x is true {  return x === true}
function isFalse(x: unknown): x is false {  return x === false}
function isType<  T extends string | { type: string },  U extends T extends { type: string } ? T["type"] : T,>(type: U) {  return (value: T): value is Extract<T, U | { type: U }> =>    (value as any) === type || (value as any).type === type}
const isInstanceMemo = new WeakMap<abstract new(...args: any) => any, Guard<unknown, any>>()function isInstance<T>(ctor: abstract new(...args: any) => T): Guard<unknown, T> {  return getOrInit(    isInstanceMemo,    ctor,    () => (value: unknown): value is T => value instanceof ctor,  )}
// Exclude<unknown, null> === unknown// SmartExclude<unknown, null> === {} | undefinedexport type SmartExclude<T1, T2 extends T1> = T2 extends null | undefined  ? T1 & Exclude<{} | null | undefined, T2>  : Exclude<T1, T2>