ClassTag-based pattern matching does not work with extractors

[smarter]

import scala.reflect.ClassTag

class A[Foo](implicit tag: ClassTag[Foo]) {
  object ExtractFoo {
    def unapply(foo: Foo): Boolean = true
  }

  def isFoo(x: Any) = x match {
    case ExtractFoo() => true
    case _ => false
  }
}

object Test {
  def main(args: Array[String]): Unit = {
    assert((new A[String]).isFoo("foo")) // OK
    assert(!(new A[String]).isFoo(42)) // OK in scalac, fails in Dotty
  }
}

The ClassTag handling is done in typedTyped but the extractor handling is done in typedUnapply where we create a Typed node using tpd.Typed which does not call typedTyped

This is needed to get the dotty-compiled shared backend to have the correct runtime behavior.