added lox test files

lox.t/closure/unused_later_closure.lox

@@ -0,0 +1,28 @@
+// This is a regression test. When closing upvalues for discarded locals, it
+// wouldn't make sure it discarded the upvalue for the correct stack slot.
+//
+// Here we create two locals that can be closed over, but only the first one
+// actually is. When "b" goes out of scope, we need to make sure we don't
+// prematurely close "a".
+var closure;
+
+{
+  var a = "a";
+
+  {
+    var b = "b";
+    fun returnA() {
+      return a;
+    }
+
+    closure = returnA;
+
+    if (false) {
+      fun returnB() {
+        return b;
+      }
+    }
+  }
+
+  print closure(); // expect: a
+}