Fix issue with dart2dart translation of parameters (collision risk).

sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart

 // 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.
 
 part of dart_backend;
 
 class LocalPlaceholder {
   final String identifier;
   final Set<Node> nodes;
   LocalPlaceholder(this.identifier) : nodes = new Set<Node>();
@@ skipping 30 matching lines @@
   DeclarationTypePlaceholder(this.typeNode, this.requiresVar);
 }
 
 class SendVisitor extends ResolvedVisitor {
   final PlaceholderCollector collector;
 
   get compiler => collector.compiler;
 
   SendVisitor(this.collector, TreeElements elements) : super(elements);
 
-  visitOperatorSend(Send node) {}
+  visitOperatorSend(Send node) {
+    if (node.isParameterCheck) {
+      final element = elements[node.receiver];
+      if (element != null) {
+        collector.tryMakeLocalPlaceholder(element, node.receiver);
+      }
+    }
+  }
+
   visitForeignSend(Send node) {}
 
   visitSuperSend(Send node) {
     Element element = elements[node];
     if (element != null && element.isConstructor()) {
       collector.makeRedirectingConstructorPlaceholder(node.selector, element);
     } else {
       collector.tryMakeMemberPlaceholder(node.selector);
     }
   }
@@ skipping 167 matching lines @@
     } else {
       assert(element is ClassElement || element is TypedefElement);
     }
     currentLocalPlaceholders = new Map<String, LocalPlaceholder>();
     compiler.withCurrentElement(element, () {
       elementNode.accept(this);
     });
   }
 
   void tryMakeLocalPlaceholder(Element element, Identifier node) {
-    bool isOptionalParameter() {
+    bool isNamedOptionalParameter() {
       FunctionElement function = element.enclosingElement;
-      for (Element parameter in function.functionSignature.optionalParameters) {
+      FunctionSignature signature = function.functionSignature;
+      if (!signature.optionalParametersAreNamed) return false;
+      for (Element parameter in signature.optionalParameters) {
         if (identical(parameter, element)) return true;
       }
       return false;
     }
 
     // TODO(smok): Maybe we should rename privates as well, their privacy
     // should not matter if they are local vars.
     if (node.source.isPrivate()) return;
-    if (element.isParameter() && isOptionalParameter()) {
+    if (element.isParameter() && isNamedOptionalParameter()) {
       currentFunctionScope.registerParameter(node);
     } else if (Elements.isLocal(element)) {
       makeLocalPlaceholder(node);
     }
   }
 
   void tryMakeMemberPlaceholder(Identifier node) {
     assert(node != null);
     if (node.source.isPrivate()) return;
     if (node is Operator) return;
@@ skipping 350 matching lines @@
 
   visitBlock(Block node) {
     for (Node statement in node.statements.nodes) {
       if (statement is VariableDefinitions) {
         makeVarDeclarationTypePlaceholder(statement);
       }
     }
     node.visitChildren(this);
   }
 }