Types

Iterable[T] = concept self
    T
    when SupportIteratorHit:
      iterator items(self): T
    else:
      when defined(js):
        typeof(self.items(), ItemTypeMode) is T
      else:
        for value in self:
          value is T

Mimic Pythons Iterable. But not checks iter Source   Edit  

Iterator[T] = concept selfof Iterable[T]
    T
    self.next is T

Source   Edit