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author | Eugene Burmako <xeno.by@gmail.com> | 2012-09-06 21:05:17 +0200 |
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committer | Eugene Burmako <xeno.by@gmail.com> | 2012-09-06 23:19:20 +0200 |
commit | 6a740332c7bfd56b20993be6ecd0bf818104f56c (patch) | |
tree | 6884bd48506c9e2468d07cfcf7433121c04cfac2 /src/library | |
parent | adf2d3632b07eef4fc2303aef994e66584a73f49 (diff) | |
download | scala-6a740332c7bfd56b20993be6ecd0bf818104f56c.tar.gz scala-6a740332c7bfd56b20993be6ecd0bf818104f56c.tar.bz2 scala-6a740332c7bfd56b20993be6ecd0bf818104f56c.zip |
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.
Diffstat (limited to 'src/library')
-rw-r--r-- | src/library/scala/reflect/ClassTag.scala | 21 |
1 files changed, 20 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[_]] |