Add a comment to HashMap.castToThat

retronym · retronym · commit 759c6d82f359 · 2020-06-25T11:21:42.000+10:00
diff --git a/library/src/scala/collection/immutable/HashMap.scala b/library/src/scala/collection/immutable/HashMap.scala
@@ -237,6 +237,9 @@ sealed class HashMap[A, +B] extends AbstractMap[A, B]
       castToThat(result)
     }
   }
+
+  // These methods exist to encapsulate the `.asInstanceOf[That]` in a slightly safer way -- only suitable values can
+  // be cast and the type of the `CanBuildFrom` guides type inference.
   private[this] def castToThat[C, That](m: HashMap[A, B])(implicit bf: CanBuildFrom[HashMap[A, B], C, That]): That = {
     m.asInstanceOf[That]
   }

Original file line number	Diff line number	Diff line change
`@@ -237,6 +237,9 @@ sealed class HashMap[A, +B] extends AbstractMap[A, B]`
`237`	`237`	`castToThat(result)`
`238`	`238`	`}`
`239`	`239`	`}`
	`240`	`+`
	`241`	+ // These methods exist to encapsulate the `.asInstanceOf[That]` in a slightly safer way -- only suitable values can
	`242`	+ // be cast and the type of the `CanBuildFrom` guides type inference.
`240`	`243`	`private[this] def castToThat[C, That](m: HashMap[A, B])(implicit bf: CanBuildFrom[HashMap[A, B], C, That]): That = {`
`241`	`244`	`m.asInstanceOf[That]`
`242`	`245`	`}`