Enable most of the constant AST serialization for AST-based summaries.

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

 // Copyright (c) 2016, 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.summarize_const_expr;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/summary/format.dart';
 
@@ skipping 45 matching lines @@
     } else if (expr is StringLiteral) {
       _serializeString(expr);
     } else if (expr is SymbolLiteral) {
       strings.add(expr.components.map((token) => token.lexeme).join('.'));
       operations.add(UnlinkedConstOperation.pushString);
       operations.add(UnlinkedConstOperation.makeSymbol);
     } else if (expr is NullLiteral) {
       operations.add(UnlinkedConstOperation.pushNull);
     } else if (expr is Identifier) {
       references.add(serializeIdentifier(expr));
+      operations.add(UnlinkedConstOperation.pushReference);
     } else if (expr is InstanceCreationExpression) {
       _serializeInstanceCreation(expr);
     } else if (expr is ListLiteral) {
       _serializeListLiteral(expr);
     } else if (expr is MapLiteral) {
       _serializeMapLiteral(expr);
     } else if (expr is MethodInvocation) {
       String name = expr.methodName.name;
       if (name != 'identical') {
         throw new _ConstExprSerializationError(
@@ skipping 196 matching lines @@
  * Error that describes a problem during a constant expression serialization.
  */
 class _ConstExprSerializationError {
   final String message;
 
   _ConstExprSerializationError(this.message);
 
   @override
   String toString() => message;
 }