options.ts

enum Option { Some = 1, Empty = 2 }
type DistributeOptionValue<T> = T extends null | undefined ? OptionValue<T, Option.Empty> : OptionValue<T, Option.Some>;
interface OptionValue<T, O extends Option> {
    option: O;
    value: T;
}

function getValue<T>(value: T): DistributeOptionValue<T>
function getValue<T>(value: T): OptionValue<T, Option> {
    return ({ 
        option: value ? Option.Some : Option.Empty, 
        value 
    });
}

type GetOptionValue<T extends OptionValue<any, Option>> =
    T extends OptionValue<infer U, infer O> ? O extends Option.Empty ? Option.Empty: U : never;

let handleSomeValue = <T extends OptionValue<any, Option>>(obj: T): GetOptionValue<T> => {
    switch (obj.option) {
        case Option.Some:
            return obj.value;
        default:
            return Option.Empty as GetOptionValue<T>;
    }
}
let someStringValue = 'check'; // type string
let result1 = handleSomeValue(getValue(someStringValue)); // it is 'string' correctly
let someNumberValue = 22;
let result2 = handleSomeValue(getValue(someNumberValue)); //is number


let someStringOrUndefinedValue: string | null | undefined = Math.random() > 0.5 ? "" : undefined;
let uu = getValue(someStringOrUndefinedValue);
let result3 = handleSomeValue(getValue(someStringOrUndefinedValue)); // is string | Option.Empty

let someUndefinedValue: undefined = undefined;
let result4 = handleSomeValue(getValue(someUndefinedValue)); // is Option.Empty