Fix #1513: misaligned by name type parameter type bounds

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/pos/t1513a.scala b/tests/pos/t1513a.scala
new file mode 100644
index 000000000..3c4c02376
--- /dev/null
+++ b/tests/pos/t1513a.scala
@@ -0,0 +1,36 @@
+object Test {
+  // Heterogeneous lists and natural numbers as defined in shapeless.
+
+  sealed trait HList
+  sealed trait ::[H, T <: HList] extends HList
+  sealed trait HNil extends HList
+
+  sealed trait Nat
+  sealed trait Succ[P <: Nat] extends Nat
+  sealed trait Zero extends Nat
+
+  // Accessor type class to compute the N'th element of an HList L.
+
+  trait Accessor[L <: HList, N <: Nat] { type Out }
+  object Accessor {
+    type Aux[L <: HList, N <: Nat, O] = Accessor[L, N] { type Out = O }
+
+    // (H :: T).At[Zero] = H
+    implicit def caseZero[H, T <: HList]: Aux[H :: T, Zero, H] = ???
+
+    // T.At[N] = O => (H :: T).At[Succ[N]] = O
+    implicit def caseN[H, T <: HList, N <: Nat, O]
+      (implicit a: Aux[T, N, O]): Aux[H :: T, Succ[N], O] = ???
+  }
+
+  case class Proxy[T]()
+
+  def at1[NN <: Nat, OO]              (implicit e: Accessor.Aux[String :: HNil, NN, OO]): OO = ???
+  def at2[NN <: Nat, OO](p: Proxy[NN])(implicit e: Accessor.Aux[String :: HNil, NN, OO]): OO = ???
+
+  // N is fixed by a value
+  at2(Proxy[Zero]): String
+
+  // N is fixed as a type parameter (by name)
+  at1[NN = Zero]: String
+}