import { isSet } from "https://deno.land/x/unknownutil@v3.18.0/mod.ts";
Return true if the type of x is Set<unknown>.
import { is } from "@core/unknownutil";
const a: unknown = new Set([0, 1, 2]);
if (is.Set(a)) {
// a is narrowed to Set<unknown>
const _: Set<unknown> = a;
}