File: genericConditionalConstrainedToUnknownNotAssignableToConcreteObject.ts

package info (click to toggle)
node-typescript 4.9.5%2Bds1-2
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 533,908 kB
  • sloc: javascript: 2,018,330; makefile: 7; sh: 1
file content (26 lines) | stat: -rw-r--r-- 502 bytes parent folder | download | duplicates (3) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
 
interface A { x: number }

declare function isA(a: unknown): a is A;

type FunctionsObj<T> = {
    [K in keyof T]: () => unknown
}

function g<
    T extends FunctionsObj<T>,
    M extends keyof T
>(a2: ReturnType<T[M]>, x: A) {
    x = a2;
}

// Original CFA report of the above issue

function g2<
    T extends FunctionsObj<T>,
    M extends keyof T
>(a2: ReturnType<T[M]>) {
    if (isA(a2)) {
        // a2 is not narrowed
        a2.x // error, but should be ok
    }
}