Constant folding of indexers

pkg/compiler/lib/src/constants/values.dart

 // Copyright (c) 2012, 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 dart2js.constants.values;
 
 import '../common.dart';
 import '../core_types.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart'
@@ skipping 484 matching lines @@
     }
     sb.write('])');
     return sb.toString();
   }
 }
 
 class MapConstantValue extends ObjectConstantValue {
   final List<ConstantValue> keys;
   final List<ConstantValue> values;
   final int hashCode;
+  Map<ConstantValue, ConstantValue> _lookupMap;
 
   MapConstantValue(InterfaceType type,
                    List<ConstantValue> keys,
                    List<ConstantValue> values)
       : this.keys = keys,
         this.values = values,
         this.hashCode = Hashing.listHash(values,
                             Hashing.listHash(keys,
                                 Hashing.objectHash(type))),
         super(type) {
@@ skipping 17 matching lines @@
 
   List<ConstantValue> getDependencies() {
     List<ConstantValue> result = <ConstantValue>[];
     result.addAll(keys);
     result.addAll(values);
     return result;
   }
 
   int get length => keys.length;
 
+  ConstantValue lookup(ConstantValue key) {
+    var lookupMap = _lookupMap ??=
+        new Map<ConstantValue, ConstantValue>.fromIterables(keys, values);
+    return lookupMap[key];
+  }
+
   accept(ConstantValueVisitor visitor, arg) => visitor.visitMap(this, arg);
 
   String unparse() {
     StringBuffer sb = new StringBuffer();
     _unparseTypeArguments(sb);
     sb.write('{');
     for (int i = 0 ; i < length ; i++) {
       if (i > 0) sb.write(',');
       sb.write(keys[i].unparse());
       sb.write(':');
@@ skipping 193 matching lines @@
 
   @override
   DartType getType(CoreTypes types) => const DynamicType();
 
   @override
   String toStructuredString() => 'NonConstant';
 
   @override
   String unparse() => '>>non-constant<<';
 }