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.

1 files changed, 36 insertions, 0 deletions

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