exhaustive switch support

[ellemedit]

type T =  "a" | "b" | "c";

const f = (t: T) => {
    switch (t) {
        case 'a': {
            return 0;
        }
        case 'b': {
            return 2;
        }
        case 'c': {
            return 1;   
        }
    }
}

enum T2 {
    a = "a",
    b = "b",
    c = "c"
}

const f2 = (t: T2) => {
    switch (t) {
        case 'a': {
            return 0;
        }
        case 'b': {
            return 2;
        }
        case 'c': {
            return 1;   
        }
    }
    return null;
}

f1 return type inferred as 0 | 1 | 2, but f2 inferred as 0 | 1 | 2 | null. TypeScript is not smart enough to infer enum type for exhaustive switch. Previous type interface supported exhaustive switch, thus developers can safely use useQuery via status. Could we rollback this?

[tannerlinsley]

Short answer is... probably not any time soon. @boschni can elaborate more on this.

[boschni]

Hi @beingbook! If you specify the actual enum in the switch cases then the exhaustive check should work :)

[ellemedit]

yes, it works with enum. but I think it might be verbose.