bug Illegal duplicate inheritance error not issued for ProductN (and other potential case class parents)

Illegal duplicate inheritance error not issued for ProductN (and other potential case class parents)

Open scabug opened this issue 10 years ago • 5 comments

I noticed this loophole when perusing fixDuplicateSyntheticParents in Typers.

scala> trait T[A]
defined trait T

scala> abstract class C(i: Int) extends T[Int] with T[String]
<console>:8: error: illegal inheritance;
 self-type C does not conform to T[Int]'s selftype T[Int]
       abstract class C(i: Int) extends T[Int] with T[String]
                                        ^
<console>:8: error: illegal inheritance;
 self-type C does not conform to T[String]'s selftype T[String]
       abstract class C(i: Int) extends T[Int] with T[String]
                                                    ^

scala> abstract class C(i: Int) extends Product1[Int] with Product1[String]
defined class C

We should easily be able to:

limit that code to case classes
remove ProductN from the list of potentially synthetic parents (as it is no longer even experimentally a case class parent)