Handle contexts which have been optimized out.

runtime/vm/deopt_instructions.cc

 // Copyright (c) 2013, 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/deopt_instructions.h"
 
 #include "vm/assembler.h"
 #include "vm/code_patcher.h"
 #include "vm/intermediate_language.h"
 #include "vm/locations.h"
@@ skipping 349 matching lines @@
 RawArray* DeoptContext::DestFrameAsArray() {
   ASSERT(dest_frame_ != NULL && dest_frame_is_allocated_);
   const Array& dest_array =
       Array::Handle(Array::New(dest_frame_size_));
   Object& obj = Object::Handle();
   for (intptr_t i = 0; i < dest_frame_size_; i++) {
     obj = reinterpret_cast<RawObject*>(dest_frame_[i]);
     ASSERT(obj.IsNull() ||
            obj.IsInstance() ||
            obj.IsContext() ||
-           obj.IsTypeArguments());
+           obj.IsTypeArguments() ||
+           obj.IsClass() ||
+           obj.IsField());

[turnidge, 2014/02/13 18:55:49]

...or I could just eliminate this ASSERT entirely...

[siva, 2014/02/13 22:58:40]

Under what circumstances can we expect to see a Class object and Field object in
a dart frame? Maybe you should add a comment here
explaining that.

[turnidge, 2014/02/14 16:36:27]

I don't know why this happened yet.  I was hoping you would know :-/.

     dest_array.SetAt(i, obj);
   }
   return dest_array.raw();
 }
 
 
 // Deoptimization instruction moving value from optimized frame at
 // 'source_index' to specified slots in the unoptimized frame.
 // 'source_index' represents the slot index of the frame (0 being
 // first argument) and accounts for saved return address, frame
@@ skipping 1032 matching lines @@
                           Smi* offset,
                           DeoptInfo* info,
                           Smi* reason) {
   intptr_t i = index * kEntrySize;
   *offset ^= table.At(i);
   *info ^= table.At(i + 1);
   *reason ^= table.At(i + 2);
 }
 
 }  // namespace dart