SI-6535 Step back from the precipice of a cycle

Adding any non-local parent to WrapAsScala will trigger a valid
cyclic reference error. By moving the import of `Wrapper._`
inside `WrapAsScala` and `WrapAsJava`, it is not in scope when
typing the parents of those, and we avoid the cycle.

Adds a test case to show the essense of the promiscious mutual
imports that triggers this.

2 files changed, 6 insertions, 2 deletions

diff --git a/src/library/scala/collection/convert/WrapAsJava.scala b/src/library/scala/collection/convert/WrapAsJava.scala
index 9115b9e5fb..5e6126a7cf 100644
--- a/src/library/scala/collection/convert/WrapAsJava.scala
+++ b/src/library/scala/collection/convert/WrapAsJava.scala
@@ -10,10 +10,11 @@ package scala.collection
 package convert
 
 import java.{ lang => jl, util => ju }, java.util.{ concurrent => juc }
-import Wrappers._
 import scala.language.implicitConversions
 
 trait WrapAsJava {
+  import Wrappers._
+
   /**
    * Implicitly converts a Scala Iterator to a Java Iterator.
    * The returned Java Iterator is backed by the provided Scala
diff --git a/src/library/scala/collection/convert/WrapAsScala.scala b/src/library/scala/collection/convert/WrapAsScala.scala
index 5a5d204ece..ffcca62291 100644
--- a/src/library/scala/collection/convert/WrapAsScala.scala
+++ b/src/library/scala/collection/convert/WrapAsScala.scala
@@ -10,11 +10,13 @@ package scala.collection
 package convert
 
 import java.{ lang => jl, util => ju }, java.util.{ concurrent => juc }
-import Wrappers._
 import scala.language.implicitConversions
 
 trait LowPriorityWrapAsScala {
   this: WrapAsScala =>
+
+  import Wrappers._
+
   /**
    * Implicitly converts a Java ConcurrentMap to a Scala mutable ConcurrentMap.
    * The returned Scala ConcurrentMap is backed by the provided Java
@@ -34,6 +36,7 @@ trait LowPriorityWrapAsScala {
 }
 
 trait WrapAsScala extends LowPriorityWrapAsScala {
+  import Wrappers._
   /**
    * Implicitly converts a Java `Iterator` to a Scala `Iterator`.
    *