Migrate UnlinkedParam.defaultValue to UnlinkedExecutable.bodyExpr.

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

Index: pkg/analyzer/lib/src/dart/element/element.dart
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index 78d0f5f496275bf18d56e98cef9fd068b33ae782..8e7ca3c3fb71c3f82740c5eaf1e09153002bc6fb 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -1827,7 +1827,7 @@ class DefaultParameterElementImpl extends ParameterElementImpl
   @override
   Expression get constantInitializer {
     if (_unlinkedParam != null) {
-      UnlinkedConst defaultValue = _unlinkedParam.defaultValue;
+      UnlinkedConst defaultValue = _unlinkedParam.initializer?.bodyExpr;
       if (defaultValue == null) {
         return null;
       }
@@ -5748,7 +5748,7 @@ class ParameterElementImpl extends VariableElementImpl
   @override
   String get defaultValueCode {
     if (_unlinkedParam != null) {
-      if (_unlinkedParam.defaultValue == null) {
+      if (_unlinkedParam.initializer?.bodyExpr == null) {
         return null;
       }
       return _unlinkedParam.defaultValueCode;