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Diffstat (limited to 'test/files/pos/t3177.scala')
-rw-r--r-- | test/files/pos/t3177.scala | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/test/files/pos/t3177.scala b/test/files/pos/t3177.scala new file mode 100644 index 0000000000..9f9528faec --- /dev/null +++ b/test/files/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 = 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(_) +}
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