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package dotty.tools.dotc
package sbt
import scala.annotation.tailrec
import scala.collection.mutable.ListBuffer
import xsbti.api
/** Create and hold thunks. A thunk is a (potentially) unevaluated value
* that may be evaluated once.
*/
private[sbt] trait ThunkHolder {
private[this] val thunks = new ListBuffer[api.Lazy[_]]
/** Force all unevaluated thunks to prevent space leaks. */
@tailrec protected final def forceThunks(): Unit = if (!thunks.isEmpty) {
val toForce = thunks.toList
thunks.clear()
toForce.foreach(_.get())
// Forcing thunks may create new thunks
forceThunks()
}
/** Store the by-name parameter `s` in a `Lazy` container without evaluating it.
* It will be forced by the next call to `forceThunks()`
*/
def lzy[T <: AnyRef](t: => T): api.Lazy[T] = {
val l = SafeLazy(() => t)
thunks += l
l
}
/** Store the parameter `s` in a `Lazy` container, since `s` is not by-name, there
* is nothing to force.
*
* TODO: Get rid of this method. It is only needed because some xsbti.api classes
* take lazy arguments when they could be strict, but this can be fixed in sbt,
* see https://github.com/sbt/zinc/issues/114
*/
def strict2lzy[T <: AnyRef](t: T): api.Lazy[T] =
SafeLazy.strict(t)
}
// TODO: Use xsbti.SafeLazy once https://github.com/sbt/zinc/issues/113 is fixed
private object SafeLazy {
def apply[T <: AnyRef](eval: () => T): xsbti.api.Lazy[T] =
new Impl(eval)
def strict[T <: AnyRef](value: T): xsbti.api.Lazy[T] =
new Strict(value)
private[this] final class Impl[T <: AnyRef](private[this] var eval: () => T) extends xsbti.api.AbstractLazy[T] {
private[this] lazy val _t = {
val t = eval()
eval = null // clear the reference, ensuring the only memory we hold onto is the result
t
}
def get: T = _t
}
private[this] final class Strict[T <: AnyRef](val get: T) extends xsbti.api.Lazy[T] with java.io.Serializable
}
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