declare function baz(): Promise<true | "a" | "b" | "c" | Error>;

async function foo() {
    let bar: "x" | Error;
    for (let i = 0; i < 3; i++) {
        const test = await baz();
        switch (test) {
            case true: return;
            case "a": throw new Error("a");
            case "b": {
                bar = "x";
                continue;
            }
            default: {
                if (test instanceof Error) {
                    bar = new Error("foo");
                    continue;
                } else {
                    throw new Error("c");
                }
            }
        }
    }
    // false positive: bar is used before being assigned
    if (bar === "x") {

    } else {
        bar.message = "something";
    }
}