Fix issue 18435.

runtime/vm/parser.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/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "platform/utils.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
@@ skipping 5369 matching lines @@
   }
 }
 
 
 // Populate local scope with the formal parameters.
 void Parser::AddFormalParamsToScope(const ParamList* params,
                                     LocalScope* scope) {
   ASSERT((params != NULL) && (params->parameters != NULL));
   ASSERT(scope != NULL);
   const int num_parameters = params->parameters->length();
+  // Formal parameters should always be the first variables of the scope.
+  if (scope->num_variables() > 0) {
+    // Any local variables already present in the scope were entered as a side
+    // effect of parsing formal parameter default values. They are aliases of
+    // variables in outer scopes.
+    scope->Clear();
+  }
   for (int i = 0; i < num_parameters; i++) {
     ParamDesc& param_desc = (*params->parameters)[i];
     ASSERT(!is_top_level_ || param_desc.type->IsResolved());
     const String* name = param_desc.name;
     LocalVariable* parameter = new LocalVariable(
         param_desc.name_pos, *name, *param_desc.type);
     if (!scope->AddVariable(parameter)) {
       ErrorMsg(param_desc.name_pos,
                "name '%s' already exists in scope",
                param_desc.name->ToCString());
@@ skipping 5549 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart