Scala idea prompt function parameters

scala list.map Use

  def main(args: Array[String]): Unit = {
      
    val list: List[(String, Int)] = List(("a", 1), ("b", 2), ("c", 3))
    //  Statistics wordcount
    val newList: List[(String, Int)] = list.map(t => {
      
      (t._1, t._2 * 2)
    })
    println(newList) //  Output  List((a,2), (b,4), (c,6))
  }

   
    

1. list.map() This function requires a parameter to be passed in , What type of parameter is this ？
   

The required parameters are Function type namely () =>{}, The parameters of this function are tuples , namely （string, int）, The return type is B( This B I don't understand )

The above complete writing is

    val newList: List[(String, Int)] = list.map((t: (String, Int)) => {
      
      (t._1, t._2 * 2)
    })

   
    

2. How to simplify it ？

Please refer to ： Anonymous functions and Simplification principle of anonymous functions