ProtoTypes#wildApprox: fix LazyRef approximation

Before this commit, the output of `wildApprox(A)` where `A <: Sys[LazyRef(A)]` was
`? <: Sys[LazyRef(() => wildApprox(A))]`. This lead to infinite
subtyping checks.

This is fixed by always approximating a LazyRef by an unbounded
wildcard. Since we only create LazyRefs when we encounter a cycle, this
should be safe.

Fix #1103.

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/pos/i1103.scala b/tests/pos/i1103.scala
new file mode 100644
index 000000000..dcc391a6a
--- /dev/null
+++ b/tests/pos/i1103.scala
@@ -0,0 +1,5 @@
+class Sys[S]
+class Foo[T <: Sys[T]] {
+  val t: T = ???
+  def foo[A <: Sys[A]](x: A = t) = x
+}