From 57b616c1a7adc78dd46cb3ae5545e312c11e69be Mon Sep 17 00:00:00 2001 From: Martin Odersky Date: Tue, 27 Jan 2015 11:38:50 +0100 Subject: New tests --- tests/pos/t3177.scala | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 tests/pos/t3177.scala (limited to 'tests/pos/t3177.scala') diff --git a/tests/pos/t3177.scala b/tests/pos/t3177.scala new file mode 100644 index 000000000..12dfce6ee --- /dev/null +++ b/tests/pos/t3177.scala @@ -0,0 +1,39 @@ +trait InvariantFunctor[F[_]] { + def xmap[A, B](ma: F[A], f: A => B, g: B => A): F[B] +} + +object InvariantFunctor { + import Endo._ + + implicit val EndoInvariantFunctor: InvariantFunctor[Endo] = new InvariantFunctor[Endo] { + def xmap[A, B](ma: Endo[A], f: A => B, g: B => A): Endo[B] = (b: B) => f(ma(g(b))) + } + + // The definition about fails with: + // anon-type.scala:9: error: not found: value b + // def xmap[A, B](ma: Endo[A], f: A => B, g: B => A): Endo[B] = (b: B) => f(ma(g(b))) + // ^ + // anon-type.scala:8: error: not found: type $anon + // implicit val EndoInvariantFunctor = new InvariantFunctor[Endo] { + // ^ + + + // These both work: + // implicit val EndoInvariantFunctorAscribed: InvariantFunctor[Endo] = new InvariantFunctor[Endo] { + // def xmap[A, B](ma: Endo[A], f: A => B, g: B => A): Endo[B] = (b: B) => f(ma(g(b))) + // } + // + // implicit val EndoInvariantFunctorStubbed = new InvariantFunctor[Endo] { + // def xmap[A, B](ma: Endo[A], f: A => B, g: B => A): Endo[B] = error("stub") + // } +} + +trait Endo[X] + +object Endo { + implicit def EndoTo[A](f: A => A): Endo[A] = new Endo[A] { + def apply(a: A) = f(a) + } + + implicit def EndoFrom[A](e: Endo[A]): A => A = e.apply(_) +} -- cgit v1.2.3