Add now-fixed test case for rdar://problem/45590743

Author: DougGregor

validation-test/compiler_crashers_2_fixed/0209-rdar45590743.swift

@@ -0,0 +1,10 @@
+// RUN: not %target-swift-frontend -typecheck %s
+
+// rdar://problem/45590743 used to crash
+class Base {
+  var x = 0
+}
+
+class Derived : Base {
+  override var x = Derived().x
+}