Implementation of null-aware operators.

pkg/compiler/lib/src/universe/universe.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 universe;
 
 import '../elements/elements.dart';
 import '../dart2jslib.dart';
 import '../dart_types.dart';
 import '../types/types.dart';
@@ skipping 526 matching lines @@
   static const Name CALL_NAME = const PublicName(Compiler.CALL_OPERATOR_NAME);
 
   Selector.internal(this.kind,
                     this.memberName,
                     this.callStructure,
                     this.hashCode) {
     assert(kind == SelectorKind.INDEX ||
            (memberName != INDEX_NAME && memberName != INDEX_SET_NAME));
     assert(kind == SelectorKind.OPERATOR ||
            kind == SelectorKind.INDEX ||
-           !Elements.isOperatorName(memberName.text));
+           !Elements.isOperatorName(memberName.text) ||
+           identical(memberName.text, '??'));
     assert(kind == SelectorKind.CALL ||
            kind == SelectorKind.GETTER ||
            kind == SelectorKind.SETTER ||
-           Elements.isOperatorName(memberName.text));
+           Elements.isOperatorName(memberName.text) ||
+           identical(memberName.text, '??'));
   }
 
   // TODO(johnniwinther): Extract caching.
   static Map<int, List<Selector>> canonicalizedValues =
       new Map<int, List<Selector>>();
 
   factory Selector(SelectorKind kind,
                    Name name,
                    CallStructure callStructure) {
     // TODO(johnniwinther): Maybe use equality instead of implicit hashing.
@@ skipping 298 matching lines @@
 
   Selector extendIfReachesAll(Compiler compiler) {
     bool canReachAll = compiler.enabledInvokeOn
         && mask.needsNoSuchMethodHandling(this, compiler.world);
     return canReachAll
         ? new TypedSelector(
             compiler.typesTask.dynamicType, this, compiler.world)
         : this;
   }
 }