Validate well-formedness of the use lists in debug mode.

runtime/vm/intermediate_language.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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 377 matching lines @@
 
 
 void UseVal::AddToEnvUseList() {
   set_next_use(definition()->env_use_list());
   definition()->set_env_use_list(this);
 }
 
 
 void Definition::ReplaceUsesWith(Definition* other) {
   ASSERT(other != NULL);
+  ASSERT(this != other);
   while (input_use_list_ != NULL) {
     UseVal* current = input_use_list_;
     input_use_list_ = input_use_list_->next_use();
     current->set_definition(other);
     current->AddToInputUseList();
   }
   while (env_use_list_ != NULL) {
     UseVal* current = env_use_list_;
     env_use_list_ = env_use_list_->next_use();
     current->set_definition(other);
@@ skipping 1119 matching lines @@
     values_.Add(UseDefinition(definitions[i]));
   }
 }
 
 
 Environment* Environment::Copy() const {
   Environment* copy = new Environment(values().length(),
                                       fixed_parameter_count());
   GrowableArray<Value*>* values_copy = copy->values_ptr();
   for (intptr_t i = 0; i < values().length(); ++i) {
-    Value* val = values()[i];
-    values_copy->Add(val->IsUse()
-                     ? UseDefinition(values()[i]->AsUse()->definition())
-                     : val);
+    values_copy->Add(values()[i]->CopyValue());
   }
   return copy;
 }
 
 
 #undef __
 
 }  // namespace dart