misleading error message when missing return value on recursive type-parametric function

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Not exactly a showstopper, but in 2.6.0-RC2, if you evaluate:

def fl1[A](l: List[List[A]])= l match {
  case List() => List[A]();
  case x :: xs => x ::: fl1(xs);
}

you get:

<console>:7: error: illegal cyclic reference involving method fl1
  case x :: xs => x ::: fl1(xs);
                    ^

Which wasn't very illuminating. I would have expected something like:

<console>:7: error: recursive method fl1 needs result type
  case x :: xs => x ::: fl1(xs);

which is what you get if you remove the type-parameterization

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Imported From: https://issues.scala-lang.org/browse/SI-34?orig=1
Reporter: Commit Message Bot (anonymous)

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@odersky said:
fixed in r13315

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@odersky said:
Milestone 2.6.1 deleted