clear the Function0 reference of Need

[xuwei-k]

inspired by sbt SafeLazy

old version xuwei-k@e52825eb3d1dbcd

[S11001001]

Is lazy val guaranteed by SLS to be implemented using an exclusive lock rather than compare-and-swap?

[larsrh]

I have no opinion on that matter, because I'm not knowledgeable enough about lazy val semantics.

[larsrh]

The test is quite dodgy, but I guess that's okay if you want to test that sort of thing :-) 👍

[larsrh]

Cannot be backported:

[error]  * synthetic method value0$1(scala.Function0,scala.runtime.ObjectRef,scala.runtime.VolatileIntRef)java.lang.Object in object scalaz.Need does not have a correspondent in new version
[error]    filter with: ProblemFilters.exclude[MissingMethodProblem]("scalaz.Need.value0$1")