Migrate UnlinkedParam.defaultValue to UnlinkedExecutable.bodyExpr.

pkg/analyzer/lib/src/summary/summarize_elements.dart

 // Copyright (c) 2015, 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 serialization.elements;
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 901 matching lines @@
       if (type is FunctionType && type.element.isSynthetic) {
         b.isFunctionTyped = true;
         b.type = serializeTypeRef(type.returnType, parameter);
         b.parameters = type.parameters
             .map((parameter) => serializeParam(parameter, context))
             .toList();
       } else {
         b.type = serializeTypeRef(type, context);
       }
     }
+    // TODO(scheglov) VariableMember.initializer is not implemented
+    if (parameter is! VariableMember && parameter.initializer != null) {
+      b.initializer = serializeExecutable(parameter.initializer);
+    }
     if (parameter is ConstVariableElement) {
       ConstVariableElement constParameter = parameter as ConstVariableElement;
       Expression initializer = constParameter.constantInitializer;
       if (initializer != null) {
-        b.defaultValue = serializeConstExpr(
+        b.initializer?.bodyExpr = serializeConstExpr(
             parameter,
             parameter.getAncestor((Element e) => e is ExecutableElement),
             initializer);
         b.defaultValueCode = parameter.defaultValueCode;
       }
     }
-    // TODO(scheglov) VariableMember.initializer is not implemented
-    if (parameter is! VariableMember && parameter.initializer != null) {
-      b.initializer = serializeExecutable(parameter.initializer);
-    }
     {
       SourceRange visibleRange = parameter.visibleRange;
       if (visibleRange != null) {
         b.visibleOffset = visibleRange.offset;
         b.visibleLength = visibleRange.length;
       }
     }
     return b;
   }
 
@@ skipping 728 matching lines @@
       exportNames.add(new LinkedExportNameBuilder(
           name: name,
           dependency: serializeDependency(dependentLibrary),
           unit: unit,
           kind: kind));
     }
     pb.exportNames = exportNames;
     return pb;
   }
 }