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unknownType1.js
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unknownType1.js
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//// [unknownType1.ts]
// In an intersection everything absorbs unknown
type T00 = unknown & null; // null
type T01 = unknown & undefined; // undefined
type T02 = unknown & null & undefined; // null & undefined (which becomes never in union)
type T03 = unknown & string; // string
type T04 = unknown & string[]; // string[]
type T05 = unknown & unknown; // unknown
type T06 = unknown & any; // any
// In a union an unknown absorbs everything
type T10 = unknown | null; // unknown
type T11 = unknown | undefined; // unknown
type T12 = unknown | null | undefined; // unknown
type T13 = unknown | string; // unknown
type T14 = unknown | string[]; // unknown
type T15 = unknown | unknown; // unknown
type T16 = unknown | any; // any
// Type variable and unknown in union and intersection
type T20<T> = T & {}; // T & {}
type T21<T> = T | {}; // T | {}
type T22<T> = T & unknown; // T
type T23<T> = T | unknown; // unknown
// unknown in conditional types
type T30<T> = unknown extends T ? true : false; // Deferred
type T31<T> = T extends unknown ? true : false; // Deferred (so it distributes)
type T32<T> = never extends T ? true : false; // true
type T33<T> = T extends never ? true : false; // Deferred
type T35<T> = T extends unknown ? { x: T } : false;
type T36 = T35<string | number>; // { x: string } | { x: number }
type T37 = T35<any>; // { x: any }
type T38 = T35<unknown>; // { x: unknown }
// keyof unknown
type T40 = keyof any; // string | number | symbol
type T41 = keyof unknown; // never
// Only equality operators are allowed with unknown
function f10(x: unknown) {
x == 5;
x !== 10;
x >= 0; // Error
x.foo; // Error
x[10]; // Error
x(); // Error
x + 1; // Error
x * 2; // Error
-x; // Error
+x; // Error
}
// No property accesses, element accesses, or function calls
function f11(x: unknown) {
x.foo; // Error
x[5]; // Error
x(); // Error
new x(); // Error
}
// typeof, instanceof, and user defined type predicates
declare function isFunction(x: unknown): x is Function;
function f20(x: unknown) {
if (typeof x === "string" || typeof x === "number") {
x; // string | number
}
if (x instanceof Error) {
x; // Error
}
if (isFunction(x)) {
x; // Function
}
}
// Homomorphic mapped type over unknown
type T50<T> = { [P in keyof T]: number };
type T51 = T50<any>; // { [x: string]: number }
type T52 = T50<unknown>; // {}
// Anything is assignable to unknown
function f21<T>(pAny: any, pNever: never, pT: T) {
let x: unknown;
x = 123;
x = "hello";
x = [1, 2, 3];
x = new Error();
x = x;
x = pAny;
x = pNever;
x = pT;
}
// unknown assignable only to itself and any
function f22(x: unknown) {
let v1: any = x;
let v2: unknown = x;
let v3: object = x; // Error
let v4: string = x; // Error
let v5: string[] = x; // Error
let v6: {} = x; // Error
let v7: {} | null | undefined = x; // Error
}
// Type parameter 'T extends unknown' not related to object
function f23<T extends unknown>(x: T) {
let y: object = x; // Error
}
// Anything but primitive assignable to { [x: string]: unknown }
function f24(x: { [x: string]: unknown }) {
x = {};
x = { a: 5 };
x = [1, 2, 3];
x = 123; // Error
}
// Locals of type unknown always considered initialized
function f25() {
let x: unknown;
let y = x;
}
// Spread of unknown causes result to be unknown
function f26(x: {}, y: unknown, z: any) {
let o1 = { a: 42, ...x }; // { a: number }
let o2 = { a: 42, ...x, ...y }; // unknown
let o3 = { a: 42, ...x, ...y, ...z }; // any
}
// Functions with unknown return type don't need return expressions
function f27(): unknown {
}
// Rest type cannot be created from unknown
function f28(x: unknown) {
let { ...a } = x; // Error
}
// Class properties of type unknown don't need definite assignment
class C1 {
a: string; // Error
b: unknown;
c: any;
}
// Type parameter with explicit 'unknown' constraint not assignable to '{}'
function f30<T, U extends unknown>(t: T, u: U) {
let x: {} = t;
let y: {} = u;
}
// Repro from #26796
type Test1 = [unknown] extends [{}] ? true : false; // false
type IsDefinitelyDefined<T extends unknown> = [T] extends [{}] ? true : false;
type Test2 = IsDefinitelyDefined<unknown>; // false
function oops<T extends unknown>(arg: T): {} {
return arg; // Error
}
//// [unknownType1.js]
"use strict";
// In an intersection everything absorbs unknown
var __assign = (this && this.__assign) || function () {
__assign = Object.assign || function(t) {
for (var s, i = 1, n = arguments.length; i < n; i++) {
s = arguments[i];
for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
t[p] = s[p];
}
return t;
};
return __assign.apply(this, arguments);
};
var __rest = (this && this.__rest) || function (s, e) {
var t = {};
for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
t[p] = s[p];
if (s != null && typeof Object.getOwnPropertySymbols === "function")
for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {
if (e.indexOf(p[i]) < 0 && Object.prototype.propertyIsEnumerable(p[i]))
t[p[i]] = s[p[i]];
}
return t;
};
// Only equality operators are allowed with unknown
function f10(x) {
x == 5;
x !== 10;
x >= 0; // Error
x.foo; // Error
x[10]; // Error
x(); // Error
x + 1; // Error
x * 2; // Error
-x; // Error
+x; // Error
}
// No property accesses, element accesses, or function calls
function f11(x) {
x.foo; // Error
x[5]; // Error
x(); // Error
new x(); // Error
}
function f20(x) {
if (typeof x === "string" || typeof x === "number") {
x; // string | number
}
if (x instanceof Error) {
x; // Error
}
if (isFunction(x)) {
x; // Function
}
}
// Anything is assignable to unknown
function f21(pAny, pNever, pT) {
var x;
x = 123;
x = "hello";
x = [1, 2, 3];
x = new Error();
x = x;
x = pAny;
x = pNever;
x = pT;
}
// unknown assignable only to itself and any
function f22(x) {
var v1 = x;
var v2 = x;
var v3 = x; // Error
var v4 = x; // Error
var v5 = x; // Error
var v6 = x; // Error
var v7 = x; // Error
}
// Type parameter 'T extends unknown' not related to object
function f23(x) {
var y = x; // Error
}
// Anything but primitive assignable to { [x: string]: unknown }
function f24(x) {
x = {};
x = { a: 5 };
x = [1, 2, 3];
x = 123; // Error
}
// Locals of type unknown always considered initialized
function f25() {
var x;
var y = x;
}
// Spread of unknown causes result to be unknown
function f26(x, y, z) {
var o1 = __assign({ a: 42 }, x); // { a: number }
var o2 = __assign({ a: 42 }, x, y); // unknown
var o3 = __assign({ a: 42 }, x, y, z); // any
}
// Functions with unknown return type don't need return expressions
function f27() {
}
// Rest type cannot be created from unknown
function f28(x) {
var a = __rest(x, []); // Error
}
// Class properties of type unknown don't need definite assignment
var C1 = /** @class */ (function () {
function C1() {
}
return C1;
}());
// Type parameter with explicit 'unknown' constraint not assignable to '{}'
function f30(t, u) {
var x = t;
var y = u;
}
function oops(arg) {
return arg; // Error
}