184 lines
4.6 KiB
TypeScript
184 lines
4.6 KiB
TypeScript
// @strict: true
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// In an intersection everything absorbs unknown
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type T00 = unknown & null; // null
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type T01 = unknown & undefined; // undefined
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type T02 = unknown & null & undefined; // never
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type T03 = unknown & string; // string
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type T04 = unknown & string[]; // string[]
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type T05 = unknown & unknown; // unknown
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type T06 = unknown & any; // any
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// In a union an unknown absorbs everything
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type T10 = unknown | null; // unknown
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type T11 = unknown | undefined; // unknown
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type T12 = unknown | null | undefined; // unknown
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type T13 = unknown | string; // unknown
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type T14 = unknown | string[]; // unknown
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type T15 = unknown | unknown; // unknown
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type T16 = unknown | any; // any
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// Type variable and unknown in union and intersection
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type T20<T> = T & {}; // T & {}
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type T21<T> = T | {}; // T | {}
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type T22<T> = T & unknown; // T
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type T23<T> = T | unknown; // unknown
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// unknown in conditional types
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type T30<T> = unknown extends T ? true : false; // Deferred
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type T31<T> = T extends unknown ? true : false; // Deferred (so it distributes)
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type T32<T> = never extends T ? true : false; // true
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type T33<T> = T extends never ? true : false; // Deferred
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type T35<T> = T extends unknown ? { x: T } : false;
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type T36 = T35<string | number>; // { x: string } | { x: number }
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type T37 = T35<any>; // { x: any }
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type T38 = T35<unknown>; // { x: unknown }
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// keyof unknown
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type T40 = keyof any; // string | number | symbol
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type T41 = keyof unknown; // never
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// Only equality operators are allowed with unknown
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function f10(x: unknown) {
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x == 5;
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x !== 10;
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x >= 0; // Error
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x.foo; // Error
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x[10]; // Error
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x(); // Error
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x + 1; // Error
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x * 2; // Error
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-x; // Error
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+x; // Error
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}
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// No property accesses, element accesses, or function calls
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function f11(x: unknown) {
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x.foo; // Error
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x[5]; // Error
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x(); // Error
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new x(); // Error
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}
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// typeof, instanceof, and user defined type predicates
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declare function isFunction(x: unknown): x is Function;
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function f20(x: unknown) {
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if (typeof x === "string" || typeof x === "number") {
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x; // string | number
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}
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if (x instanceof Error) {
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x; // Error
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}
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if (isFunction(x)) {
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x; // Function
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}
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}
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// Homomorphic mapped type over unknown
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type T50<T> = { [P in keyof T]: number };
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type T51 = T50<any>; // { [x: string]: number }
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type T52 = T50<unknown>; // {}
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// Anything is assignable to unknown
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function f21<T>(pAny: any, pNever: never, pT: T) {
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let x: unknown;
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x = 123;
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x = "hello";
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x = [1, 2, 3];
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x = new Error();
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x = x;
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x = pAny;
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x = pNever;
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x = pT;
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}
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// unknown assignable only to itself and any
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function f22(x: unknown) {
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let v1: any = x;
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let v2: unknown = x;
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let v3: object = x; // Error
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let v4: string = x; // Error
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let v5: string[] = x; // Error
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let v6: {} = x; // Error
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let v7: {} | null | undefined = x; // Error
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}
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// Type parameter 'T extends unknown' not related to object
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function f23<T extends unknown>(x: T) {
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let y: object = x; // Error
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}
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// Anything fresh but primitive assignable to { [x: string]: unknown }
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function f24(x: { [x: string]: unknown }) {
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x = {};
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x = { a: 5 };
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x = [1, 2, 3]; // Error
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x = 123; // Error
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}
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// Locals of type unknown always considered initialized
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function f25() {
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let x: unknown;
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let y = x;
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}
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// Spread of unknown causes result to be unknown
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function f26(x: {}, y: unknown, z: any) {
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let o1 = { a: 42, ...x }; // { a: number }
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let o2 = { a: 42, ...x, ...y }; // unknown
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let o3 = { a: 42, ...x, ...y, ...z }; // any
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let o4 = { a: 42, ...z }; // any
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}
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// Functions with unknown return type don't need return expressions
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function f27(): unknown {
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}
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// Rest type cannot be created from unknown
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function f28(x: unknown) {
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let { ...a } = x; // Error
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}
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// Class properties of type unknown don't need definite assignment
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class C1 {
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a: string; // Error
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b: unknown;
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c: any;
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}
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// Type parameter with explicit 'unknown' constraint not assignable to '{}'
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function f30<T, U extends unknown>(t: T, u: U) {
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let x: {} = t;
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let y: {} = u;
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}
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// Repro from #26796
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type Test1 = [unknown] extends [{}] ? true : false; // false
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type IsDefinitelyDefined<T extends unknown> = [T] extends [{}] ? true : false;
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type Test2 = IsDefinitelyDefined<unknown>; // false
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function oops<T extends unknown>(arg: T): {} {
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return arg; // Error
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}
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