Add clause for HKApply in TypeAssigner#avoid

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/pos/tcpoly_infer_ticket474.scala b/tests/pos/tcpoly_infer_ticket474.scala
new file mode 100644
index 000000000..9012deb2b
--- /dev/null
+++ b/tests/pos/tcpoly_infer_ticket474.scala
@@ -0,0 +1,27 @@
+trait Builder[C[_], T] {
+  def +=(x: T): Unit
+  def finalise: C[T]
+}
+
+trait Buildable[C[_]] {
+  def builder[T]: Builder[C,T]
+}
+
+object Test {
+
+  implicit object buildableList extends Buildable[List] {
+    def builder[T] = new Builder[List,T] {
+      val buf = new scala.collection.mutable.ListBuffer[T]
+      def +=(x: T) = buf += x
+      def finalise = buf.toList
+    }
+  }
+
+  def foo[C[_],T](x: T)(implicit b: Buildable[C]): C[T] = {
+    val builder = b.builder[T]
+    builder += x
+    builder.finalise
+  }
+
+  val l: List[Int] = foo(8)
+}