by sinoon @sinoon
タプルTを受け取り、そのタプルの長さを返す型Length<T>を実装します。
例えば
type tesla = ['tesla', 'model 3', 'model X', 'model Y']
type spaceX = ['FALCON 9', 'FALCON HEAVY', 'DRAGON', 'STARSHIP', 'HUMAN SPACEFLIGHT']
type teslaLength = Length<tesla> // expected 4
type spaceXLength = Length<spaceX> // expected 5
