Prune constraints that could turn into cycles

Fixes #864. Review by @smarter.

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/pos/i864.scala b/tests/pos/i864.scala
new file mode 100644
index 000000000..8d2b85999
--- /dev/null
+++ b/tests/pos/i864.scala
@@ -0,0 +1,10 @@
+object C {
+  val a: Int = 1
+  val b: Int = 2
+  val c: Int = 2
+
+  trait X[T]
+  implicit def u[A, B]: X[A | B] = new X[A | B] {}
+  def y[T](implicit x: X[T]): T = ???
+  val x: a.type & b.type | b.type & c.type = y
+}