VM: Fix incorrect debug assertion.

runtime/vm/jit_optimizer.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/jit_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 3100 matching lines @@
   const String& field_name =
       String::Handle(Z, Field::NameFromSetter(instr->function_name()));
   const Field& field =
       Field::ZoneHandle(Z, GetField(class_id, field_name));
   ASSERT(!field.IsNull());
 
   if (InstanceCallNeedsClassCheck(instr, RawFunction::kImplicitSetter)) {
     AddReceiverCheck(instr);
   }
   if (field.guarded_cid() != kDynamicCid) {
-    ASSERT(!FLAG_use_field_guards);
+    ASSERT(FLAG_use_field_guards);
     InsertBefore(instr,
                  new(Z) GuardFieldClassInstr(
                      new(Z) Value(instr->ArgumentAt(1)),
                       field,
                       instr->deopt_id()),
                  instr->env(),
                  FlowGraph::kEffect);
   }
 
   if (field.needs_length_check()) {
-    ASSERT(!FLAG_use_field_guards);
+    ASSERT(FLAG_use_field_guards);
     InsertBefore(instr,
                  new(Z) GuardFieldLengthInstr(
                      new(Z) Value(instr->ArgumentAt(1)),
                       field,
                       instr->deopt_id()),
                  instr->env(),
                  FlowGraph::kEffect);
   }
 
   // Field guard was detached.
@@ skipping 10 matching lines @@
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
   ReplaceCall(instr, store);
   return true;
 }
 
 
 }  // namespace dart