Fix #830: Compiler hangs on implicit search with singleton &/|

In fact we get a deep subtype recursion when compileing i830.scala. The problem
goes away once we make use of the fact that the intersection of two singleton
types which are not subtypes of each other is empty.

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/pos/i830.scala b/tests/pos/i830.scala
new file mode 100644
index 000000000..8fcb29f36
--- /dev/null
+++ b/tests/pos/i830.scala
@@ -0,0 +1,6 @@
+object C {
+  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: 1 & 2 | 2 & 3 = y
+}