tuple.ts

// copy from https://github.com/microsoft/TypeScript/issues/13298#issuecomment-513813788

type Overwrite<T, S extends any> = {[P in keyof T]: S[P]};
type TupleUnshift<T extends any[], X> = T extends any ? ((x: X, ...t: T) => void) extends (...t: infer R) => void ? R : never : never;
type TuplePush<T extends any[], X> = T extends any
    ? Overwrite<TupleUnshift<T, any>, T & {[x: string]: X}>
    : never;