Migrate UnlinkedParam.defaultValue to UnlinkedExecutable.bodyExpr.

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

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 432d414429e37d6438a6d5b4c028092784acfbeb..7c924741bc925ce56a26143e73cd88bde007659a 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -919,21 +919,21 @@ class _CompilationUnitSerializer {
         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) {