Typesafe string concat

stringConcat.ts

export type StringConcat<TArgs extends string[]> = _Flatten<TArgs>;

type _Flatten<TArgs extends string[], _TArg extends string = ""> =
  TArgs extends [infer TCurrent extends string, ...infer TNext extends string[]]
    ? _Flatten<TNext, `${_TArg}${TCurrent}`>
    : _TArg;

export function stringConcat<const TArgs extends string[]>(...args: TArgs): StringConcat<TArgs> {
  if (args.length === 0) return "" as StringConcat<TArgs>;
  return "".concat(...args) as StringConcat<TArgs>;
}