Use correct scope to lookup saved async context variable.

runtime/vm/scopes.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/scopes.h"
 
 #include "vm/object.h"
 #include "vm/stack_frame.h"
 #include "vm/symbols.h"
 
@@ skipping 414 matching lines @@
 }
 
 
 bool LocalScope::CaptureVariable(const String& name) {
   ASSERT(name.IsSymbol());
   LocalScope* current_scope = this;
   while (current_scope != NULL) {
     LocalVariable* var = current_scope->LocalLookupVariable(name);
     if (var != NULL) {
       var->set_is_captured();
-      // Insert aliases of the variable in intermediate scopes.
-      LocalScope* intermediate_scope = this;
-      while (intermediate_scope != current_scope) {
-        intermediate_scope->variables_.Add(var);
-        ASSERT(var->owner() != intermediate_scope);  // Item is an alias.
-        intermediate_scope = intermediate_scope->parent();
+      LocalScope* scope = this;
+      while (var->owner()->function_level() != scope->function_level()) {
+        // Insert an alias of the variable in the top scope of each function
+        // level so that the variable is found in the context.
+        LocalScope* parent_scope = scope->parent();
+        while ((parent_scope != NULL) &&
+               (parent_scope->function_level() == scope->function_level())) {
+          scope = parent_scope;
+          parent_scope = scope->parent();
+        }
+        scope->variables_.Add(var);
+        ASSERT(var->owner() != scope);  // Item is an alias.
+        scope = parent_scope;
       }
       return true;
     }
     current_scope = current_scope->parent();
   }
   return false;
 }
 
 
 SourceLabel* LocalScope::LookupLabel(const String& name) {
@@ skipping 233 matching lines @@
     return fixed_parameter_count - (index() - kParamEndSlotFromFp);
   } else {
     // Shift negative indexes so that the lowest one is 0 (they are still
     // non-positive).
     return fixed_parameter_count - (index() - kFirstLocalSlotFromFp);
   }
 }
 
 
 }  // namespace dart