uhm....

REPL

Welcome to Scala 2.12.6 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_162).
Type in expressions for evaluation. Or try :help.

scala> case class Meep(msb: Long, lsb: Long)
defined class Meep

scala> case class Moop(value: Meep) extends AnyVal
defined class Moop

scala> case class Whee(moop: Moop, whoop: String)
defined class Whee

scala> def f[A <: AnyVal { def value: Meep }](as: A*): Seq[Long] = as.map(_.value.msb)
f: [A <: AnyVal{def value: Meep}](as: A*)Seq[Long]

scala> f(Moop(Meep(1, 2)))
res0: Seq[Long] = ArrayBuffer(1)

scala> def g[A <: AnyVal { def value: Meep }](things: { def moop: A }*): Seq[Long] = things.map(_.moop.value.msb)
g: [A <: AnyVal{def value: Meep}](things: AnyRef{def moop: A}*)Seq[Long]

scala> g(Whee(Moop(Meep(1, 2)), "eh"))
java.lang.NoSuchMethodException: Meep.value()
  at java.lang.Class.getMethod(Class.java:1786)
  at .reflMethod$Method1(<console>:13)
  at .$anonfun$g$1(<console>:13)
  at .$anonfun$g$1$adapted(<console>:13)
  at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:234)
  at scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:32)
  at scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:29)
  at scala.collection.mutable.WrappedArray.foreach(WrappedArray.scala:38)
  at scala.collection.TraversableLike.map(TraversableLike.scala:234)
  at scala.collection.TraversableLike.map$(TraversableLike.scala:227)
  at scala.collection.AbstractTraversable.map(Traversable.scala:104)
  at .g(<console>:13)
  ... 28 elided