export interface ReadonlySetFromArrayC<C extends t.Mixed>
  extends t.Type<ReadonlySet<t.TypeOf<C>>, ReadonlyArray<t.OutputOf<C>>, unknown> {}

export function readonlySetFromArray<C extends t.Mixed>(
  codec: C,
  O: Ord<t.TypeOf<C>>,
  name: string = `ReadonlySet<${codec.name}>`
): ReadonlySetFromArrayC<C> { ... }