Fix for issue #28287 (Illegal argument in isolate message : (object is a regular Dart Instance))

runtime/vm/snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
@@ skipping 1119 matching lines @@
       if (objref->IsType()) {
         typeobj ^= objref->raw();
         newobj = typeobj.Canonicalize();
       } else {
         ASSERT(objref->IsTypeArguments());
         typeargs ^= objref->raw();
         newobj = typeargs.Canonicalize();
       }
       if (newobj.raw() != objref->raw()) {
         ZoneGrowableArray<intptr_t>* patches = backref.patch_records();
-        ASSERT(newobj.IsCanonical());
+        ASSERT(newobj.IsNull() || newobj.IsCanonical());
         ASSERT(patches != NULL);
         // First we replace the back ref table with the canonical object.
         *objref = newobj.raw();
         // Now we go over all the patch records and patch the canonical object.
         for (intptr_t j = 0; j < patches->length(); j += 2) {
           NoSafepointScope no_safepoint;
           intptr_t patch_object_id = (*patches)[j];
           intptr_t patch_offset = (*patches)[j + 1];
           Object* target = GetBackRef(patch_object_id);
           // We should not backpatch an object that is canonical.
@@ skipping 805 matching lines @@
   if (setjmp(*jump.Set()) == 0) {
     NoSafepointScope no_safepoint;
     WriteObject(obj.raw());
   } else {
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart