Enabled variance checking

Variance checking is now run as part of type-checking.

Fixed tests that exhibited variance errors. Added tests where some classes of
variance errors should be detected.

3 files changed, 5 insertions, 2 deletions

diff --git a/tests/pos/t1843.scala b/tests/pos/t1843.scala
index e9b5c5d2d..5e8554a93 100644
--- a/tests/pos/t1843.scala
+++ b/tests/pos/t1843.scala
@@ -5,7 +5,7 @@
 */
 
 object Crash {
-  trait UpdateType[A]
+  trait UpdateType[+A]
   case class StateUpdate[+A](updateType : UpdateType[A], value : A)
   case object IntegerUpdateType extends UpdateType[Integer]
 
diff --git a/tests/pos/typers.scala b/tests/pos/typers.scala
index a95af558e..b2d786c1c 100644
--- a/tests/pos/typers.scala
+++ b/tests/pos/typers.scala
@@ -32,7 +32,7 @@ object typers {
   }
 
   class List[+T] {
-    def :: (x: T) = new :: (x, this)
+    def :: [U >: T](x: U): List[U] = new :: (x, this)
 
     def len: Int = this match {
       case x :: xs1 => 1 + xs1.len
diff --git a/tests/pos/variances.scala b/tests/pos/variances.scala
new file mode 100644
index 000000000..db858fd5d
--- /dev/null
+++ b/tests/pos/variances.scala
@@ -0,0 +1,3 @@
+trait C[+T <: C[T, U], -U <: C[T, U]] {
+
+}