Fix basic_scoping.js compiler test

See the added comments for more details.

Tests/FuzzilliTests/CompilerTests/basic_scoping.js

@@ -16,12 +16,21 @@ function foo(x) {
   }
   output(x);
   output(y);
-  let obj = { x: 45, y: 9001 };
-  with (obj) {
-    output(x);
-    output(y);
-  }
+}
+foo(44);
+
+// Note: this test will currently fail if 'a' and 'b' are replaced by
+// 'x' and 'y' in the object. That's because the compiler will still used
+// regular/numbered variables for x and y, and so will effectively rename
+// them to something like `v1` and `v2`, while keeping the property names
+// of the object. This isn't easy to fix, unfortunately. One option might
+// be to change the compiler to only use named variables in testcases that
+// use `with` statements, but that would be quite an invasive change and
+// result in a FuzzIL program that is less suited for mutations.
+let obj = { a: 45, b: 9001 };
+with (obj) {
   output(x);
   output(y);
+  output(a);
+  output(b);
 }
-foo(44);