case classes not nice towards language.existentials

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Welcome to Scala version 2.10.0-RC3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_07).
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scala> case class A(c: Class[_])
<console>:7: warning: inferred existential type Option[Class[_$1]] forSome { type _$1 }, which cannot be expressed by wildcards,  should be enabled
by making the implicit value language.existentials visible.
This can be achieved by adding the import clause 'import scala.language.existentials'
or by setting the compiler option -language:existentials.
See the Scala docs for value scala.language.existentials for a discussion
why the feature should be explicitly enabled.
       case class A(c: Class[_])
                  ^
defined class A

scala> object B { def x: Option[Class[_]] = null }
defined module B

My prime guess would be that the synthesized unapply method lacks a proper type ascription.

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Imported From: https://issues.scala-lang.org/browse/SI-6798?orig=1
Reporter: @rkuhn
Affected Versions: 2.10.0-RC1
Duplicates #6541

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@retronym said (edited on Dec 11, 2012 4:33:36 PM UTC):
Duplicate of #6541