Fix-#1500 Include constraining type variables when interpolating

Fixes #1500. Review by @smarter.

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/pos/i1500.scala b/tests/pos/i1500.scala
new file mode 100644
index 000000000..713d06689
--- /dev/null
+++ b/tests/pos/i1500.scala
@@ -0,0 +1,19 @@
+sealed trait HList
+sealed trait HNil extends HList
+sealed trait ::[+H, +T <: HList] extends HList
+
+case class Size[L <: HList](value: Int)
+
+object Size {
+  implicit val caseHNil: Size[HNil] = Size(0)
+  implicit def caseHCons[H, T <: HList](implicit e: Size[T]): Size[H :: T] = Size(e.value + 1)
+}
+
+object HListTest {
+  def main(args: Array[String]): Unit = {
+    assert(implicitly[Size[HNil]].value == 0)
+    assert(implicitly[Size[Int :: HNil]].value == 1)
+    assert(implicitly[Size[Int :: Int :: HNil]].value == 2)
+    assert(implicitly[Size[Int :: Int :: Int :: HNil]].value == 3)
+  }
+}