#TypeScript: Does anyone know why and how to fix it?
I want new Map(arr1) to have the inferred(!) type Map<typeof Red | typeof Green, "RED" | "GREEN">
new Map(arr2) does have a nice inferred type, so this should be possible(?)
const Red = Symbol('Red');
const Green = Symbol('Green');
const arr1 = [
[Red, 'RED'],
[Green, 'GREEN'],
] as const;
new Map(arr1); // error
const arr2 = [
[0, 'RED'],
[1, 'GREEN'],
] as const;
new Map(arr2); // OK
@rauschma
If filing a bug with the TS team, this might be helpful to add.
const arr3 = [
[Red as typeof Red | typeof Green, 'RED'],
[Green as typeof Red | typeof Green, 'GREEN'],
] as const;
new Map(arr3); // OK
@MildlyAggrievedScientist Cool, thanks! Do you have a link?
I found a workaround:
type Key = (typeof arr1)[number][0];
new Map<Key, string>(arr1);
Inferring the Map key is important to me because I want to check statically if all cases were covered.
Axel Rauschmayer
Stuart Schechter