Lower bound must be a subtype of the upper bound.

The change in CommonSupertypes:

 We used to say that commonSupertype(Inv<A>, Inv<B>) = Inv<in Intersect(A, B)). This is counter-intuitive, should be Inv<out commonSupertype(A, B)>

compiler/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java

@@ -200,6 +200,8 @@ public class JetTypeCheckerTest extends JetLiteFixture {
         assertCommonSupertype("Base_T<in Int>", "Derived_T<Int>", "Base_T<in Int>");
         assertCommonSupertype("Base_T<in Int>", "Derived_T<in Int>", "Base_T<Int>");
         assertCommonSupertype("Base_T<*>", "Base_T<Int>", "Base_T<*>");
+
+        assertCommonSupertype("Base_T<out Parent>", "Base_T<A>", "Base_T<B>");
     }
 
     public void testIntersect() throws Exception {