convert_error.ts

async function thisGetsCalled(): Promise<string> {
    throw new Error("bla");
}

function convert(error: any) {
    throw new Error("different");
}

async function main() {
    // this is not working, error TS2322: Type 'string | void' is not assignable to type 'string'.
    // Type 'void' is not assignable to type 'string'.
    const result: string = await thisGetsCalled().catch(convert);

    // this is working, but i would have to declare let result2 before the try, to work with it later
    try {
        const result2: string = await thisGetsCalled();
    } catch (error) {
        convert(error);
    }
    // this is working (though i don't know why..) but i would prefer await style, there are more calls to follow.
    thisGetsCalled()
        .catch((error: any) => { throw new Error("different"); })
        .then((result3: string) => console.log(result3));

}

solution: function convert(error: any): never { ... }