Dotty Documentation

0.3.0-bin-SNAPSHOT

Changed: Lazy Vals and @volatile

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Lazy val initialization no longer guarantees safe publishing. This change was done to avoid the performance overhead of thread synchonization because many lazy vals are only used in a single-threaded context.

To get back safe publishing you need to annotate a lazy val with @volatile. In

@volatile lazy val x = expr

it is guaranteed that readers of a lazy val will see the value of x once it is assigned.

The ScalaFix rewrite tool as well as Dotty's own -language:Scala2 -rewrite option will rewrite all normal lazy vals to volatile ones in order to keep their semantics compatible with current Scala's.