The return type of the index in DataTransferItemList (lib.d.ts) should be DataTransferItem and not File

[mtestrot]

current Definition:

interface DataTransferItemList {
    length: number;
    add(data: File): DataTransferItem;
    clear(): void;
    item(index: number): File;
    remove(index: number): void;
    [index: number]: File;
}

should be:

interface DataTransferItemList {
    length: number;
    add(data: File): DataTransferItem;
    clear(): void;
    item(index: number): DataTransferItem;  // changed
    remove(index: number): void;
    [index: number]: DataTransferItem;         // changed
}

cf. Spec at https://html.spec.whatwg.org/multipage/interaction.html#datatransferitemlist

[zhengbli]

@mtestrot You are welcomed to contribute to the lib.d.ts bugs :) ! The instruction is at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes