BFE.devでのAI解答例 - TypeScript タイプパズル
59. implement MapStringUnionToObjectUnion<U>

type MapStringUnionToObjectUnion<U extends string> =  U extends never ? never : { value: U };

Explanation:

The MapStringUnionToObjectUnion takes a string union as its generic type parameter. We can use the conditional type to check if the type extends never. If it does, we return never to indicate there are no possible object unions. If it does not, we return an object type with a single property value which has a value of the original input type. This object type becomes one of the possible object unions in the resulting type.