SI-6318 fixes ClassTag.unapply for primitives

ClassTag.unapply now has overloads for primitive value classes
so that it can preserve boxiness when performing subtyping tests.

First I wanted to annotate ClassTag.unapply with a ClassTag itself,
i.e. to transform its signature from "def unapply(x: Any): Option[T]"
to "def unapply[U: ClassTag](x: U): Option[T]".

But then virtpatmat_typetag.scala exhibited a nasty problem.
When pattern matching with this unapply, patmat first infers U as something
and then tries to pattern match against this inferred type. And if U gets
inferred as an abstract type itself, bad things happen:
warning: The outer reference in this type test cannot be checked at run time.

That's why I decided to drop the ClassTag idea and go with 9 extra overloads.
Not very beautiful, but definitely robust.

5 files changed, 145 insertions, 1 deletions

diff --git a/src/library/scala/reflect/ClassTag.scala b/src/library/scala/reflect/ClassTag.scala
index 5255c44f10..8ce06d611e 100644
--- a/src/library/scala/reflect/ClassTag.scala
+++ b/src/library/scala/reflect/ClassTag.scala
@@ -54,7 +54,26 @@ trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with Serial
    * `SomeExtractor(...)` is turned into `ct(SomeExtractor(...))` if `T` in `SomeExtractor.unapply(x: T)`
    * is uncheckable, but we have an instance of `ClassTag[T]`.
    */
-  def unapply(x: Any): Option[T] = if (x != null && runtimeClass.isAssignableFrom(x.getClass)) Some(x.asInstanceOf[T]) else None
+  def unapply(x: Any): Option[T] = unapply_impl(x)
+  def unapply(x: Byte): Option[T] = unapply_impl(x)
+  def unapply(x: Short): Option[T] = unapply_impl(x)
+  def unapply(x: Char): Option[T] = unapply_impl(x)
+  def unapply(x: Int): Option[T] = unapply_impl(x)
+  def unapply(x: Long): Option[T] = unapply_impl(x)
+  def unapply(x: Float): Option[T] = unapply_impl(x)
+  def unapply(x: Double): Option[T] = unapply_impl(x)
+  def unapply(x: Boolean): Option[T] = unapply_impl(x)
+  def unapply(x: Unit): Option[T] = unapply_impl(x)
+
+  private def unapply_impl[U: ClassTag](x: U): Option[T] =
+    if (x == null) None
+    else {
+      val staticClass = classTag[U].runtimeClass
+      val dynamicClass = x.getClass
+      val effectiveClass = if (staticClass.isPrimitive) staticClass else dynamicClass
+      val conforms = runtimeClass.isAssignableFrom(effectiveClass)
+      if (conforms) Some(x.asInstanceOf[T]) else None
+    }
 
   /** case class accessories */
   override def canEqual(x: Any) = x.isInstanceOf[ClassTag[_]]
diff --git a/test/files/run/t6318_derived.check b/test/files/run/t6318_derived.check
new file mode 100644
index 0000000000..ad43b6579b
--- /dev/null
+++ b/test/files/run/t6318_derived.check
@@ -0,0 +1,3 @@
+Some(X)

+true

+Some(X)

diff --git a/test/files/run/t6318_derived.scala b/test/files/run/t6318_derived.scala
new file mode 100644
index 0000000000..ccdc18daee
--- /dev/null
+++ b/test/files/run/t6318_derived.scala
@@ -0,0 +1,15 @@
+import scala.reflect.{ClassTag, classTag}
+
+object Test extends App {
+  def test[T: ClassTag](x: T) {
+    println(classTag[T].runtimeClass.isAssignableFrom(x.getClass))
+    println(classTag[T].unapply(x))
+  }
+
+  class X(val x: Int) extends AnyVal { override def toString = "X" }
+  val x = new X(1)
+  // the commented line crashes because of SI-6326
+  //println(classTag[X].runtimeClass.isAssignableFrom(x.getClass))
+  println(classTag[X].unapply(x))
+  test(x)
+}
\ No newline at end of file
diff --git a/test/files/run/t6318_primitives.check b/test/files/run/t6318_primitives.check
new file mode 100644
index 0000000000..bb474c3bdc
--- /dev/null
+++ b/test/files/run/t6318_primitives.check
@@ -0,0 +1,36 @@
+true

+Some(1)

+false

+None

+true

+Some(1)

+false

+None

+true

+Some(
)

+false

+None

+true

+Some(1)

+false

+None

+true

+Some(1)

+false

+None

+true

+Some(1.0)

+false

+None

+true

+Some(1.0)

+false

+None

+true

+Some(true)

+false

+None

+true

+Some(())

+false

+None

diff --git a/test/files/run/t6318_primitives.scala b/test/files/run/t6318_primitives.scala
new file mode 100644
index 0000000000..30f27120b3
--- /dev/null
+++ b/test/files/run/t6318_primitives.scala
@@ -0,0 +1,71 @@
+import scala.reflect.{ClassTag, classTag}
+
+object Test extends App {
+  def test[T: ClassTag](x: T) {
+    println(classTag[T].runtimeClass.isAssignableFrom(x.getClass))
+    println(classTag[T].unapply(x))
+  }
+
+  {
+    val x = 1.toByte
+    println(ClassTag.Byte.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Byte.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toShort
+    println(ClassTag.Short.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Short.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toChar
+    println(ClassTag.Char.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Char.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toInt
+    println(ClassTag.Int.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Int.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toLong
+    println(ClassTag.Long.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Long.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toFloat
+    println(ClassTag.Float.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Float.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = 1.toDouble
+    println(ClassTag.Double.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Double.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = true
+    println(ClassTag.Boolean.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Boolean.unapply(x))
+    test(x)
+  }
+
+  {
+    val x = ()
+    println(ClassTag.Unit.runtimeClass.isAssignableFrom(x.getClass))
+    println(ClassTag.Unit.unapply(x))
+    test(x)
+  }
+}
\ No newline at end of file