Consider the following union type:
type T = {} | ({ some: number } & { any: string })
If you want to narrow this type to the latter, simply excluding the empty object won't work:
type WithEntries = Exclude<T, {}>
This will result in never.
Is there a different approach to achieve this narrowing?
Here is the code snippet:
type T = {} | ({ some: number } & { any: string })
type X<T> = T extends {} ? ({} extends T ? never : T) : never;
type WithEntries = X<T>; // { some: number; } & { any: string; }
In this code, the first condition distributes parts of the union type to set up for the second condition which filters out the empty type by converting it to never. This results in a union of never or non-empty parts of T, ultimately simplifying the union to just the non-empty parts of T.
This concept was inspired by this related answer.
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