Add an XFAILed test for if expressions resulting in boxes

src/test/run-pass/expr-if-box.rs

@@ -0,0 +1,14 @@
+// xfail-boot
+// xfail-stage0
+// -*- rust -*-
+
+// Tests for if as expressions returning boxed types
+
+fn test_box() {
+  auto res = if (true) { @100 } else { @101 };
+  check (*res == 100);
+}
+
+fn main() {
+  test_box();
+}