Fix val-to-val test assertions to match conservative might_reference_actor

make_might_reference_actor currently always returns true, so immutable
tracing recurses into fields. The test incorrectly assumed it would skip
field recursion for non-actor fields.

Author: SeanTAllen

test/full-program-tests/codegen-trace-val-to-val-through-trait/main.pony

@@ -29,13 +29,13 @@ actor Main is Receiver
 
   be receive(b: B val) =>
     let map_after = @gc_local(this)
-    // Both sender and receiver trace b as IMMUTABLE (val). Since B has no
-    // actor fields (might_reference_actor is false), immutable tracing does
-    // not recurse into fields. So b gets rc bookkeeping but b.a does not
-    // appear in the object map at all.
+    // Both sender and receiver trace b as IMMUTABLE (val).
+    // make_might_reference_actor is currently conservative (always true), so
+    // immutable tracing recurses into fields just like mutable tracing. Both
+    // b and b.a get rc bookkeeping.
     let ok = @objectmap_has_object_rc(map_before, b, USize(1)) and
-      not @objectmap_has_object(map_before, b.a) and
+      @objectmap_has_object_rc(map_before, b.a, USize(1)) and
       @objectmap_has_object_rc(map_after, b, USize(0)) and
-      not @objectmap_has_object(map_after, b.a)
+      @objectmap_has_object_rc(map_after, b.a, USize(0))
     @gc_local_snapshot_destroy(map_before)
     @pony_exitcode(I32(if ok then 1 else 0 end))