add parentheses for lambda param

[xuwei-k]

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Helpful things

Fixes

Purpose

prepare Scala 3

scala> Option(1).map{ a => a }
val res0: Option[Int] = Some(1)

scala> Option(1).map{ a: Int => a }
1 |Option(1).map{ a: Int => a }
  |                      ^
  |parentheses are required around the parameter of a lambda
  |This construct can be rewritten automatically under -rewrite -source 3.0-migration.

Background Context

References