Add test case

Author: liufengyun

tests/init/neg/i4031.scala

@@ -0,0 +1,10 @@
+object App {
+  trait A { type L >: Any}
+  def upcast(a: A, x: Any): a.L = x
+  val p: A { type L <: Nothing } = p        // error
+  def coerce(x: Any): Int = upcast(p, x)
+
+  def main(args: Array[String]): Unit = {
+    println(coerce("Uh oh!"))
+  }
+}

tests/init/neg/i50.scala

@@ -0,0 +1,5 @@
+class C[T] {
+  val a: T = method
+  def method = b
+  val b: T = a     // error
+}