Migrate UnlinkedParam.defaultValue to UnlinkedExecutable.bodyExpr.

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

Index: pkg/analyzer/lib/src/summary/summarize_ast.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_ast.dart b/pkg/analyzer/lib/src/summary/summarize_ast.dart
index 7c359c3e0eebf0e49fb4498a2d5cae9a714f19dd..139a4c2175fb12de7852baa99dae5c58f2d80147 100644
--- a/pkg/analyzer/lib/src/summary/summarize_ast.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_ast.dart
@@ -1044,15 +1044,15 @@ class _SummarizeAstVisitor extends RecursiveAstVisitor {
   UnlinkedParamBuilder visitDefaultFormalParameter(
       DefaultFormalParameter node) {
     UnlinkedParamBuilder b = node.parameter.accept(this);
+    b.initializer = serializeInitializerFunction(node.defaultValue);
     if (node.defaultValue != null) {
       // Closures can't appear inside default values, so we don't need a
       // localClosureIndexMap.
       Map<int, int> localClosureIndexMap = null;
-      b.defaultValue =
+      b.initializer?.bodyExpr =
           serializeConstExpr(localClosureIndexMap, node.defaultValue);
       b.defaultValueCode = node.defaultValue.toSource();
     }
-    b.initializer = serializeInitializerFunction(node.defaultValue);
     b.codeRange = serializeCodeRange(node);
     return b;
   }