Fixes an inconsistency between BoxesRunTime and Predef's autoboxing

Previously autoboxing implicits in Predef were inconsistent with
BoxesRunTime box/unbox due to different treatment of unboxing of
nulls. Implicits didn't check for null and would crash with NPE
unlike the BoxesRunTime which correctly returned zero value of
given type.

The fix is trivial: lets just use asInstanceOfs to implement
implicits in Predef. This would ensure that both have the same
behaviour and that the two would not diverge again in the future.

1 files changed, 35 insertions, 0 deletions

diff --git a/test/junit/scala/PredefAutoboxingTest.scala b/test/junit/scala/PredefAutoboxingTest.scala
new file mode 100644
index 0000000000..e5d8ded5d4
--- /dev/null
+++ b/test/junit/scala/PredefAutoboxingTest.scala
@@ -0,0 +1,35 @@
+package scala
+
+import org.junit.Test
+import org.junit.Assert._
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+import scala.tools.testing.AssertUtil._
+
+@RunWith(classOf[JUnit4])
+class PredefAutoboxingTest {
+  @Test def unboxNullByte() =
+    assertEquals(Predef.Byte2byte(null), 0.toByte)
+
+  @Test def unboxNullShort() =
+    assertEquals(Predef.Short2short(null), 0.toShort)
+
+  @Test def unboxNullCharacter() =
+    assertEquals(Predef.Character2char(null), 0.toChar)
+
+  @Test def unboxNullInteger() =
+    assertEquals(Predef.Integer2int(null), 0)
+
+  @Test def unboxNullLong() =
+    assertEquals(Predef.Long2long(null), 0L)
+
+  @Test def unboxNullFloat() =
+    assertEquals(Predef.Float2float(null), 0F, 0F)
+
+  @Test def unboxNullDouble() =
+    assertEquals(Predef.Double2double(null), 0D, 0D)
+
+  @Test def unboxNullBoolean() =
+    assertEquals(Predef.Boolean2boolean(null), false)
+}