unknownControlFlow.errors.txt

tests/cases/conformance/types/unknown/unknownControlFlow.ts(18,9): error TS2322: Type 'unknown' is not assignable to type '{}'.
tests/cases/conformance/types/unknown/unknownControlFlow.ts(283,5): error TS2536: Type 'keyof (T & {})' cannot be used to index type 'T'.
tests/cases/conformance/types/unknown/unknownControlFlow.ts(290,11): error TS2345: Argument of type 'string' is not assignable to parameter of type 'never'.
tests/cases/conformance/types/unknown/unknownControlFlow.ts(291,5): error TS2345: Argument of type 'null' is not assignable to parameter of type 'never'.
tests/cases/conformance/types/unknown/unknownControlFlow.ts(293,5): error TS2345: Argument of type 'null' is not assignable to parameter of type 'never'.


==== tests/cases/conformance/types/unknown/unknownControlFlow.ts (5 errors) ====
    type T01 = {} & string;  // string
    type T02 = {} & 'a';  // 'a'
    type T03 = {} & object;  // object
    type T04 = {} & { x: number };  // { x: number }
    type T05 = {} & null;  // never
    type T06 = {} & undefined;  // never
    type T07 = undefined & void;  // undefined
    
    type T10 = string & {};  // Specially preserved
    type T11 = number & {};  // Specially preserved
    type T12 = bigint & {};  // Specially preserved
    
    type ThisNode = {};
    type ThatNode = {};
    type ThisOrThatNode = ThisNode | ThatNode;
    
    function f01(u: unknown) {
        let x1: {} = u;  // Error
            ~~
!!! error TS2322: Type 'unknown' is not assignable to type '{}'.
        let x2: {} | null | undefined = u;
        let x3: {} | { x: string } | null | undefined = u;
        let x4: ThisOrThatNode | null | undefined = u;
    }
    
    function f10(x: unknown) {
        if (x) {
            x;  // {}
        }
        else {
            x;  // unknown
        }
        if (!x) {
            x;  // unknown
        }
        else {
            x;  // {}
        }
    }
    
    function f11<T>(x: T) {
        if (x) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (!x) {
            x;  // T
        }
        else {
            x;  // T & {}
        }
    }
    
    function f12<T extends {}>(x: T) {
        if (x) {
            x;  // T
        }
        else {
            x;  // T
        }
    }
    
    function f20(x: unknown) {
        if (x !== undefined) {
            x;  // {} | null
        }
        else {
            x;  // undefined
        }
        if (x !== null) {
            x;  // {} | undefined
        }
        else {
            x;  // null
        }
        if (x !== undefined && x !== null) {
            x;  // {}
        }
        else {
            x;  // null | undefined
        }
        if (x != undefined) {
            x;  // {}
        }
        else {
            x;  // null | undefined
        }
        if (x != null) {
            x;  // {}
        }
        else {
            x;  // null | undefined
        }
    }
    
    function f21<T>(x: T) {
        if (x !== undefined) {
            x;  // T & ({} | null)
        }
        else {
            x;  // T
        }
        if (x !== null) {
            x;  // T & ({} | undefined)
        }
        else {
            x;  // T
        }
        if (x !== undefined && x !== null) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (x != undefined) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (x != null) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
    }
    
    function f22<T extends {} | undefined>(x: T) {
        if (x !== undefined) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (x !== null) {
            x;  // T
        }
        else {
            x;  // T
        }
        if (x !== undefined && x !== null) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (x != undefined) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
        if (x != null) {
            x;  // T & {}
        }
        else {
            x;  // T
        }
    }
    
    function f23<T>(x: T | undefined | null) {
        if (x !== undefined) {
            x;  // T & {} | null
        }
        if (x !== null) {
            x;  // T & {} | undefined
        }
        if (x != undefined) {
            x;  // T & {}
        }
        if (x != null) {
            x;  // T & {}
        }
    }
    
    function f30(x: {}) {
        if (typeof x === "object") {
            x;  // object
        }
    }
    
    function f31<T>(x: T) {
        if (typeof x === "object") {
            x;  // T & object | T & null
        }
        if (x && typeof x === "object") {
            x;  // T & object
        }
        if (typeof x === "object" && x) {
            x;  // T & object
        }
    }
    
    function f32<T extends {} | undefined>(x: T) {
        if (typeof x === "object") {
            x;  // T & object
        }
    }
    
    function possiblyNull<T>(x: T) {
        return !!true ? x : null;  // T | null
    }
    
    function possiblyUndefined<T>(x: T) {
        return !!true ? x : undefined;  // T | undefined
    }
    
    function possiblyNullOrUndefined<T>(x: T) {
        return possiblyUndefined(possiblyNull(x));  // T | null | undefined
    }
    
    function ensureNotNull<T>(x: T) {
        if (x === null) throw Error();
        return x;  // T & ({} | undefined)
    }
    
    function ensureNotUndefined<T>(x: T) {
        if (x === undefined) throw Error();
        return x;  // T & ({} | null)
    }
    
    function ensureNotNullOrUndefined<T>(x: T) {
        return ensureNotUndefined(ensureNotNull(x));  // T & {}
    }
    
    function f40(a: string | undefined, b: number | null | undefined) {
        let a1 = ensureNotNullOrUndefined(a);  // string
        let b1 = ensureNotNullOrUndefined(b);  // number
    }
    
    type QQ<T> = NonNullable<NonNullable<NonNullable<T>>>;
    
    function f41<T>(a: T) {
        let a1 = ensureNotUndefined(ensureNotNull(a));  // T & {}
        let a2 = ensureNotNull(ensureNotUndefined(a));  // T & {}
        let a3 = ensureNotNull(ensureNotNull(a));  // T & {} | T & undefined
        let a4 = ensureNotUndefined(ensureNotUndefined(a));  // T & {} | T & null
        let a5 = ensureNotNullOrUndefined(ensureNotNullOrUndefined(a));  // T & {}
        let a6 = ensureNotNull(possiblyNullOrUndefined(a));  // T & {} | undefined
        let a7 = ensureNotUndefined(possiblyNullOrUndefined(a));  // T & {} | null
        let a8 = ensureNotNull(possiblyUndefined(a));  // T & {} | undefined
        let a9 = ensureNotUndefined(possiblyNull(a));  // T & {} | null
    }
    
    // Repro from #48468
    
    function deepEquals<T>(a: T, b: T): boolean {
        if (typeof a !== 'object' || typeof b !== 'object' || !a || !b) {
            return false;
        }
        if (Array.isArray(a) || Array.isArray(b)) {
            return false;
        }
        if (Object.keys(a).length !== Object.keys(b).length) { // Error here
            return false;
        }
        return true;
    }
    
    // Repro from #49386
    
    function foo<T>(x: T | null) {
        let y = x;
        if (y !== null) {
            y;
        }
    }
    
    // We allow an unconstrained object of a generic type `T` to be indexed by a key of type `keyof T`
    // without a check that the object is non-undefined and non-null. This is safe because `keyof T`
    // is `never` (meaning no possible keys) for any `T` that includes `undefined` or `null`.
    
    function ff1<T>(t: T, k: keyof T) {
        t[k];
    }
    
    function ff2<T>(t: T & {}, k: keyof T) {
        t[k];
    }
    
    function ff3<T>(t: T, k: keyof (T & {})) {
        t[k];  // Error
        ~~~~
!!! error TS2536: Type 'keyof (T & {})' cannot be used to index type 'T'.
    }
    
    function ff4<T>(t: T & {}, k: keyof (T & {})) {
        t[k];
    }
    
    ff1(null, 'foo');  // Error
              ~~~~~
!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'never'.
    ff2(null, 'foo');  // Error
        ~~~~
!!! error TS2345: Argument of type 'null' is not assignable to parameter of type 'never'.
    ff3(null, 'foo');
    ff4(null, 'foo');  // Error
        ~~~~
!!! error TS2345: Argument of type 'null' is not assignable to parameter of type 'never'.
    
    // Repro from #49681
    
    type Foo = { [key: string]: unknown };
    type NullableFoo = Foo | undefined;
    
    type Bar<T extends NullableFoo> = NonNullable<T>[string];
    
    // Generics and intersections with {}
    
    function fx0<T>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    function fx1<T extends unknown>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    function fx2<T extends {}>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    function fx3<T extends {} | undefined>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    function fx4<T extends {} | null>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    function fx5<T extends {} | null | undefined>(value: T & ({} | null)) {
        if (value === 42) {
            value;  // T & {}
        }
        else {
            value;  // T & ({} | null)
        }
    }
    
    // Double-equals narrowing
    
    function fx10(x: string | number, y: number) {
        if (x == y) {
            x;  // string | number
        }
        else {
            x;  // string | number
        }
        if (x != y) {
            x;  // string | number
        }
        else {
            x;  // string | number
        }
    }
    
    // Repros from #50706
    
    function SendBlob(encoding: unknown) {
        if (encoding !== undefined && encoding !== 'utf8') {
            throw new Error('encoding');
        }
        encoding;
    };
    
    function doSomething1<T extends unknown>(value: T): T {
        if (value === undefined) {
            return value;
        }
        if (value === 42) {
            throw Error('Meaning of life value');
        }
        return value;
    }
    
    function doSomething2(value: unknown): void {
        if (value === undefined) {
            return;
        }
        if (value === 42) {
            value;
        }
    }
    
    // Repro from #51009
    
    type TypeA = {
        A: 'A',
        B: 'B',
    }
    
    type TypeB = {
        A: 'A',
        B: 'B',
        C: 'C',
    }
    
    type R<T extends keyof TypeA> =
        T extends keyof TypeB ? [TypeA[T], TypeB[T]] : never
    
    type R2<T extends PropertyKey> =
        T extends keyof TypeA ?
        T extends keyof TypeB ?
            [TypeA[T], TypeB[T]] : never: never
    
    // Repro from #51041
    
    type AB = "A" | "B"
    
    function x<T_AB extends AB>(x: T_AB & undefined, y: any) {
        let r2: never = y as T_AB & undefined;
    }