Clone AST nodes of default formal parameters prior to constant evaluation.

pkg/analyzer/lib/src/generated/element.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.element;
 
 import 'dart:collection';
@@ skipping 2047 matching lines @@
    * to work when the argument types are type variables.
    */
   DartType substitute2(
       List<DartType> argumentTypes, List<DartType> parameterTypes);
 }
 
 /**
  * A [FieldFormalParameterElementImpl] for parameters that have an initializer.
  */
 class DefaultFieldFormalParameterElementImpl
-    extends FieldFormalParameterElementImpl {
+    extends FieldFormalParameterElementImpl with ConstVariableElement {

[Brian Wilkerson, 2015/05/05 22:43:02]

I can't check the code right now, but if "ConstVariableElement" and
"PotentiallyConstVariableElement" are not instantiated, perhaps replacing
"Element" with "Mixin" would help make their use more clear.

[Paul Berry, 2015/05/06 15:35:14]

They're not instantiated directly, but they're used in a lot of places other
than "with" clauses, e.g. in the RHS of "as" expressions, as generic parameters
to collection classes, and in "implements" clauses.

If we wanted to make things clearer I would be more inclined to turn these into
abstract classes and move their implementations to brand new "Mixin" classes. 
That way most of the usages would still point to the "...Element" interfaces,
and only the usages in the "with" clauses would point to the "...Mixin" classes.
 But I'm not sure the benefit would be worth the effort.  Let me know if you
think it's worth trying.

[Brian Wilkerson, 2015/05/06 15:46:06]

Given that ConstVariableElement and PotentiallyConstVariableElement are *not*
part of the public API, I don't think it's worth the effort. Sorry for the
noise.

   /**
    * The result of evaluating this variable's initializer.
    */
   EvaluationResultImpl _result;
 
   /**
    * Initialize a newly created parameter element to have the given [name].
    */
   DefaultFieldFormalParameterElementImpl(Identifier name) : super(name);
 
   @override
   EvaluationResultImpl get evaluationResult => _result;
 
   @override
   void set evaluationResult(EvaluationResultImpl result) {
     this._result = result;
   }
 }
 
 /**
  * A [ParameterElement] for parameters that have an initializer.
  */
-class DefaultParameterElementImpl extends ParameterElementImpl {
+class DefaultParameterElementImpl extends ParameterElementImpl
+    with ConstVariableElement {
   /**
    * The result of evaluating this variable's initializer.
    */
   EvaluationResultImpl _result;
 
   /**
    * Initialize a newly created parameter element to have the given [name].
    */
   DefaultParameterElementImpl(Identifier name) : super.forNode(name);
 
@@ skipping 6234 matching lines @@
    * A parameter will only define other parameters if it is a function typed
    * parameter.
    */
   List<ParameterElement> get parameters;
 }
 
 /**
  * A concrete implementation of a [ParameterElement].
  */
 class ParameterElementImpl extends VariableElementImpl
-    implements ParameterElement {
+    with PotentiallyConstVariableElement implements ParameterElement {
   /**
    * An empty list of parameter elements.
    */
   @deprecated // Use ParameterElement.EMPTY_LIST
   static const List<ParameterElement> EMPTY_ARRAY = const <ParameterElement>[];
 
   /**
    * A list containing all of the parameters defined by this parameter element.
    * There will only be parameters if this parameter is a function typed
    * parameter.
@@ skipping 2000 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }