Merge pull request scala/scala#10134 from SethTisue/valueof-implicitnotfound

Author: SethTisue

library/src/scala/ValueOf.scala

@@ -17,7 +17,10 @@ package scala
  * single inhabitant. Eligible types are singleton types of the form `stablePath.type`,
  * Unit and singleton types corresponding to value literals.
  *
- * Instances of `ValueOf[T]` are provided implicitly for all eligible types. Typically
+ * The value itself can conveniently be retrieved with [[Predef#valueOf]], which requires
+ * a `ValueOf` to be available in implicit scope.
+ *
+ * The compiler provides instances of `ValueOf[T]` for all eligible types. Typically
  * an instance would be required where a runtime value corresponding to a type level
  * computation is needed.
 
@@ -48,5 +51,5 @@ package scala
  * is required in the implementation of `+` it is provided at the call site via the
  * implicit argument `m` of type `ValueOf[M]`.
  */
-@scala.annotation.implicitNotFound(msg = "No singleton value available for ${T}.")
+@scala.annotation.implicitNotFound(msg = "No singleton value available for ${T}; eligible singleton types for `ValueOf` synthesis include literals and stable paths.")
 final class ValueOf[T](val value: T) extends AnyVal