Add tests related to variance checking.

Author: sstucki

tests/neg/Variances.scala

@@ -0,0 +1,15 @@
+trait HasY { type Y }
+
+// These are neg-tests corresponding to the pos-test Variances.scala
+// where all the variance annotations have been inverted.
+trait Foo1[+X] { def bar[Y <: X](y: Y) = y } // error
+trait Foo2[+X] { def bar(x: HasY { type Y <: X })(y: x.Y) = y } // error
+trait Foo3[-X] { def bar[Y >: X](y: Y) = y } // error
+trait Foo4[-X] { def bar(x: HasY { type Y >: X })(y: x.Y) = y } // error
+
+// These are neg-tests corresponding to the pos-test Variances.scala
+// where all the bounds have been flipped.
+trait Foo5[-X] { def bar[Y >: X](y: Y) = y } // error
+trait Foo6[-X] { def bar(x: HasY { type Y >: X })(y: x.Y) = y } // error
+trait Foo7[+X] { def bar[Y <: X](y: Y) = y } // error
+trait Foo8[+X] { def bar(x: HasY { type Y <: X })(y: x.Y) = y } // error

tests/pos/Variances.scala

@@ -0,0 +1,15 @@
+trait HasY { type Y }
+
+// This works in scalac.
+trait Foo1[-X] { def bar[Y <: X](y: Y) = y }
+
+// A variant of the Foo1 using a dependent method type (doesn't work
+// using scalac)
+trait Foo2[-X] { def bar(x: HasY { type Y <: X })(y: x.Y) = y }
+
+// This works in scalac.
+trait Foo3[+X] { def bar[Y >: X](y: Y) = y }
+
+// A variant of the Foo4 using a dependent method type (doesn't work
+// using scalac)
+trait Foo4[+X] { def bar(x: HasY { type Y >: X })(y: x.Y) = y }