Incorrectly supported auto-tupling for case classes

## Minimized code

```Scala
case class Foo(a: Int, b: Int)

object Test {
  def foo(x: Foo) = List(x).map(_ + _)
  
  def main(args: Array[String]): Unit = println(foo(Foo(3, 4)))
}
```

## Output

The code compiles and runs.

## Expectation

The code should be rejected, as in Scala 2.
