Typescript optional generic with extends

Question

I would like to write generic that is optional (the D in example below) and extends an interface. I can't figure out the syntax.

interface IUpdateItems {
   _id: string;
}

export const deleteItem = <T extends IUpdateItems, D = void extends IUpdateItems >(
   items: T[],
   itemToDelete: T | D
): T[] => {
   return items.filter((item) => item._id !== itemToDelete._id);
};

Answer 1

The correct syntax would look like this:

export const deleteItem = <T extends IUpdateItems, D extends IUpdateItems = never>(
   items: T[],
   itemToDelete: T | D
): T[] => {
   return items.filter((item) => item._id !== itemToDelete._id);
};

You should also replace void with never since void is not assignable to IUpdateItems causing an error.

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