@type t() :: %Riichi.Decomposer.RegularHand{
  blocks: [Riichi.Decomposer.block()] | nil,
  pair: (Riichi.Decomposer.pair() | nil) | nil,
  waiting_kind: Riichi.Decomposer.waiting_kind() | nil,
  waiting_tiles: [Riichi.Tile.t()] | nil
}