gistfile1.txt

function sum<T extends number | bigint>(a: T, b: T): T extends number ? number : bigint {
    // @ts-expect-error
    return a + b;
}

function sumo(a: number, b: number): number;
function sumo(a: bigint, b: bigint): bigint;
function sumo(a: number | bigint, b: number | bigint): number | bigint {
    // @ts-expect-error
    return a + b;
}

console.log(sum(100, 200));
console.log(sum(100n, 200n));
console.log(sum(100, 300));
let n: number | bigint = 400n;
if (Math.random() <= 0.5) {
    n = 400;
}
console.log(sum(n, 800n));