From ef536f00d9d480f28db3093b9dc09a90041cfb74 Mon Sep 17 00:00:00 2001 From: Dmitry Petrashko Date: Thu, 25 Jun 2015 09:45:27 +0200 Subject: Enable 61 tests that succeed. --- tests/run/t7200.scala | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 tests/run/t7200.scala (limited to 'tests/run/t7200.scala') diff --git a/tests/run/t7200.scala b/tests/run/t7200.scala new file mode 100644 index 000000000..8f33d016f --- /dev/null +++ b/tests/run/t7200.scala @@ -0,0 +1,34 @@ +import language.higherKinds + +object Test extends dotty.runtime.LegacyApp { + + // Slice of comonad is where this came up + trait Foo[F[_]] { + def coflatMap[A, B](f: F[A] => B): F[A] => F[B] + } + + // A non-empty list + case class Nel[A](head: A, tail: List[A]) + + object NelFoo extends Foo[Nel] { + + // It appears that the return type for recursive calls is not inferred + // properly, yet no warning is issued. Providing a return type or + // type arguments for the recursive call fixes the problem. + + def coflatMap[A, B](f: Nel[A] => B) = // ok w/ return type + l => Nel(f(l), l.tail match { + case Nil => Nil + case h :: t => { + val r = coflatMap(f)(Nel(h, t)) // ok w/ type args + r.head :: r.tail + } + }) + } + + // Without a recursive call all is well, but with recursion we get a + // ClassCastException from Integer to Nothing + NelFoo.coflatMap[Int, Int](_.head + 1)(Nel(1, Nil)) // Ok + NelFoo.coflatMap[Int, Int](_.head + 1)(Nel(1, List(2))) // CCE + +} -- cgit v1.2.3