Fix issue 18435 (2nd attempt).

runtime/vm/scopes.h

 // 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.
 
 #ifndef VM_SCOPES_H_
 #define VM_SCOPES_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "vm/allocation.h"
@@ skipping 216 matching lines @@
   void set_end_token_pos(intptr_t value) { end_token_pos_ = value; }
 
   // The number of variables allocated in the context and belonging to this
   // scope and to its children at the same loop level.
   int num_context_variables() const { return num_context_variables_; }
 
   // Add a variable to the scope. Returns false if a variable with the
   // same name is already present.
   bool AddVariable(LocalVariable* variable);
 
+  // Insert a formal parameter variable to the scope at the given position,
+  // possibly in front of aliases already added with AddVariable.
+  // Returns false if a variable with the same name is already present.
+  bool InsertParameterAt(intptr_t pos, LocalVariable* parameter);
+
   // Add a label to the scope. Returns false if a label with the same name
   // is already present.
   bool AddLabel(SourceLabel* label);
 
   // Lookup a variable in this scope only.
   LocalVariable* LocalLookupVariable(const String& name) const;
 
   // Lookup a label in this scope only.
   SourceLabel* LocalLookupLabel(const String& name) const;
 
@@ skipping 110 matching lines @@
   // List of names referenced in this scope and its children that
   // are not resolved to local variables.
   GrowableArray<NameReference*> referenced_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCOPES_H_