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

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

Index: pkg/analyzer/lib/src/generated/element.dart
diff --git a/pkg/analyzer/lib/src/generated/element.dart b/pkg/analyzer/lib/src/generated/element.dart
index 46b6d03597939adbb415d161f411cd2b9686fec3..e0a7e3133f9f71adef55cc3b02c37e870766956a 100644
--- a/pkg/analyzer/lib/src/generated/element.dart
+++ b/pkg/analyzer/lib/src/generated/element.dart
@@ -2065,7 +2065,7 @@ abstract class DartType {
  * 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.
    */
@@ -2088,7 +2088,8 @@ class DefaultFieldFormalParameterElementImpl
 /**
  * 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.
    */
@@ -8343,7 +8344,7 @@ abstract class ParameterElement implements LocalElement, VariableElement {
  * A concrete implementation of a [ParameterElement].
  */
 class ParameterElementImpl extends VariableElementImpl
-    implements ParameterElement {
+    with PotentiallyConstVariableElement implements ParameterElement {
   /**
    * An empty list of parameter elements.
    */