Added test that should cover all code paths of the changes done in SI-6220

This test will pass even with an older version of the scala library, since as mentioned this is just a performance improvement.

1 files changed, 92 insertions, 0 deletions

diff --git a/test/files/run/t6220.scala b/test/files/run/t6220.scala
new file mode 100644
index 0000000000..834b692f43
--- /dev/null
+++ b/test/files/run/t6220.scala
@@ -0,0 +1,92 @@
+import scala.collection.immutable._
+
+object Test extends App {
+
+  // finds an int x such that improved(x) differs in the first bit to improved(0),
+  // which is the worst case for the HashTrieSet
+  def findWorstCaseInts() {
+    // copy of improve from HashSet
+    def improve(hcode: Int) = {
+      var h: Int = hcode + ~(hcode << 9)
+      h = h ^ (h >>> 14)
+      h = h + (h << 4)
+      h ^ (h >>> 10)
+    }
+
+    // find two hashes which have a large separation
+    val x = 0
+    var y = 1
+    val ix = improve(x)
+    while(y!=0 && improve(y)!=ix+(1<<31))
+      y+=1
+    printf("%s %s %x %x\n",x,y,improve(x), improve(y))
+  }
+  // this is not done every test run since it would slow down ant test.suite too much.
+  // findWorstCaseInts()
+
+  // two numbers that are immediately adiacent when fed through HashSet.improve
+  val h0 = 0
+  val h1 = 1270889724
+
+  // h is the hashcode, i is ignored for the hashcode but relevant for equality
+  case class Collision(h:Int, i:Int) {
+    override def hashCode = h
+  }
+  val a = Collision(h0,0)
+  val b = Collision(h0,1)
+  val c = Collision(h1,0)
+
+  // create a HashSetCollision1
+  val x = HashSet(a) + b
+  if(x.getClass.getSimpleName != "HashSetCollision1")
+    println("x should be a collision")
+  StructureTests.validate(x)
+  // StructureTests.printStructure(x)
+  require(x.size==2 && x.contains(a) && x.contains(b))
+
+  // go from a HashSetCollision1 to a HashTrieSet with maximum depth
+  val y = x + c
+  if(y.getClass.getSimpleName != "HashTrieSet")
+    println("y should be a HashTrieSet")
+  StructureTests.validate(y)
+  // StructureTests.printStructure(y)
+  require(y.size==3 && y.contains(a) && y.contains(b) && y.contains(c))
+
+  // go from a HashSet1 directly to a HashTrieSet with maximum depth
+  val z = HashSet(a) + c
+  if(y.getClass.getSimpleName != "HashTrieSet")
+    println("y should be a HashTrieSet")
+  StructureTests.validate(z)
+  // StructureTests.printStructure(z)
+  require(z.size == 2 && z.contains(a) && z.contains(c))
+}
+
+package scala.collection.immutable {
+  object StructureTests {
+    def printStructure(x:HashSet[_], prefix:String="") {
+      x match {
+        case m:HashSet.HashTrieSet[_] =>
+          println(prefix+m.getClass.getSimpleName + " " + m.size)
+          m.elems.foreach(child => printStructure(child, prefix + "  "))
+        case m:HashSet.HashSetCollision1[_] =>
+          println(prefix+m.getClass.getSimpleName + " " + m.ks.size)
+        case m:HashSet.HashSet1[_] =>
+          println(prefix+m.getClass.getSimpleName + " " + m.head)
+        case _ =>
+          println(prefix+"empty")
+      }
+    }
+
+    def validate(x:HashSet[_]) {
+      x match {
+        case m:HashSet.HashTrieSet[_] =>
+          require(m.elems.size>1 || (m.elems.size==1 && m.elems(0).isInstanceOf[HashSet.HashTrieSet[_]]))
+          m.elems.foreach(validate _)
+        case m:HashSet.HashSetCollision1[_] =>
+          require(m.ks.size>1)
+        case m:HashSet.HashSet1[_] =>
+        case _ =>
+      }
+    }
+  }
+}