Fix insertAfter

Once the context-bounds desugaring of i1765.scala was fixed, another problem came up:
We hit an invalid denotation due to some interaction between mixin and memoize.

It turned out that `insertInsteadOf` did not do what its doc comment claimed: it did
not store a forwarding pointer `nextInRun` in the overwritten denotation. Once that
was fixed we also needed to fix a follow-on erorr that now we could have chains of
invalid denotations linked by `nextInRun`.

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/pos/i1765.scala b/tests/pos/i1765.scala
new file mode 100644
index 000000000..d79129638
--- /dev/null
+++ b/tests/pos/i1765.scala
@@ -0,0 +1,21 @@
+trait T[X]
+
+trait U[X]
+
+trait TC[M[_]] {
+  def foo[M[_]: TC, A](ma: U[A]) = ()
+  implicit val TCofT: TC[T] = new TC[T] {}
+  implicit def any2T[A](a: A): T[A] = new T[A] {}
+  implicit def any2U[A](a: A): U[A] = new U[A] {}
+  val x = foo[T, Int](1)
+  val y = ()
+}
+
+// Minimized version exhibiting an assertion violation in Denotation#current at phase lambdalift:
+trait TC2 {
+//  implicit val TCofT: TC2[T] = new TC2[T] {}
+  val TCofT: Object = {
+    class C extends TC2
+    new Object
+  }
+}