Order the parameters of a function at the definition site.

lib/compiler/implementation/elements/elements.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.
 
 #library('elements');
 
 #import('dart:uri');
 
 #import('../tree/tree.dart');
 #import('../scanner/scannerlib.dart');
@@ skipping 927 matching lines @@
 
 // TODO(johnniwinther): [FunctionSignature] should be merged with
 // [FunctionType].
 class FunctionSignature {
   final Link<Element> requiredParameters;
   final Link<Element> optionalParameters;
   final DartType returnType;
   final int requiredParameterCount;
   final int optionalParameterCount;
   final bool optionalParametersAreNamed;
+
+  List<Element> _orderedOptionalParameters;
+
   FunctionSignature(this.requiredParameters,
                     this.optionalParameters,
                     this.requiredParameterCount,
                     this.optionalParameterCount,
                     this.optionalParametersAreNamed,
                     this.returnType);
 
   void forEachRequiredParameter(void function(Element parameter)) {
     for (Link<Element> link = requiredParameters;
          !link.isEmpty();
          link = link.tail) {
       function(link.head);
     }
   }
 
   void forEachOptionalParameter(void function(Element parameter)) {
     for (Link<Element> link = optionalParameters;
          !link.isEmpty();
          link = link.tail) {
       function(link.head);
     }
   }
 
+  List<Element> get orderedOptionalParameters {
+    if (_orderedOptionalParameters != null) return _orderedOptionalParameters;
+    List<Element> list = new List<Element>.from(optionalParameters);
+    if (optionalParametersAreNamed) {
+      list.sort((Element a, Element b) {
+        return a.name.slowToString().compareTo(b.name.slowToString());
+      });
+    }
+    _orderedOptionalParameters = list;
+    return list;
+  }
+
   void forEachParameter(void function(Element parameter)) {
     forEachRequiredParameter(function);
     forEachOptionalParameter(function);
   }
 
+  void orderedForEachParameter(void function(Element parameter)) {
+    forEachRequiredParameter(function);
+    orderedOptionalParameters.forEach(function);
+  }
+
   int get parameterCount => requiredParameterCount + optionalParameterCount;
 }
 
 class FunctionElement extends Element {
   FunctionExpression cachedNode;
   DartType type;
   final Modifiers modifiers;
 
   FunctionSignature functionSignature;
 
@@ skipping 825 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }