Add test case for SI-4835 (https://issues.scala-lang.org/browse/SI-4835)

This test case only confirm that StreamIterator's lazyiness is not broken.
Test case about memory consumption could be created.  However, such a
test cause a greatly increased time of test.

2 files changed, 45 insertions, 0 deletions

diff --git a/test/files/run/t4835.check b/test/files/run/t4835.check
new file mode 100644
index 0000000000..531c3d7bb6
--- /dev/null
+++ b/test/files/run/t4835.check
@@ -0,0 +1,7 @@
+-1 0 1 2 3 4 5 6 7 8 9

+-1 1 3 5 7 9 11 13 15 17 19

+1 1

+2 1 2

+2 1 A 2

+3 1 2 3

+3 1 A 2 B 3

diff --git a/test/files/run/t4835.scala b/test/files/run/t4835.scala
new file mode 100644
index 0000000000..50d161be40
--- /dev/null
+++ b/test/files/run/t4835.scala
@@ -0,0 +1,38 @@
+/*

+ * Test case for SI-4835.  This tests confirm that the fix

+ * doesn't break laziness.  To test memory consumption, 

+ * I need to confirm that OutOfMemoryError doesn't occur.

+ * I could create such tests.  However, such tests consume

+ * too much time and memory.

+ */

+object Test {

+  private final val INFINITE = -1

+  def testStreamIterator(num: Int, stream: Stream[Int]): Unit = {

+    val iter = stream.iterator

+    print(num)

+    // if num == -1, then steram is infinite sequence

+    if (num == INFINITE) {

+      for(i <- 0 until 10) {

+        print(" " + iter.next())

+      }

+    } else {

+      while(iter.hasNext) {

+        print(" " + iter.next())

+      }

+    }

+    println()

+  }

+

+  def main(args: Array[String]): Unit = {

+    import Stream.{from, cons, empty}

+    testStreamIterator(INFINITE, from(0))

+    testStreamIterator(INFINITE, from(0).filter(_ % 2 == 1))

+    testStreamIterator(1, Stream(1))

+    testStreamIterator(2, Stream(1, 2))

+    //Stream with side effect

+    testStreamIterator(2, cons(1, cons({ print(" A"); 2}, empty)))

+    testStreamIterator(3, Stream(1, 2, 3))

+    //Stream with side effect

+    testStreamIterator(3, cons(1, cons({ print(" A"); 2}, cons({ print(" B"); 3}, Stream.empty))))

+  }

+}