Handle deferred access as pre-step in SemanticSendVisitor.

pkg/compiler/lib/src/resolution/semantic_visitor.dart

 // Copyright (c) 2015, 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.semantics_visitor;
 
 import '../constants/expressions.dart';
 import '../dart2jslib.dart' show invariant, MessageKind;
 import '../dart_types.dart';
 import '../elements/elements.dart';
@@ skipping 4037 matching lines @@
   ///   }
   ///   m() => C(true, 42);
   ///
   R visitConstructorIncompatibleInvoke(
       NewExpression node,
       ConstructorElement constructor,
       InterfaceType type,
       NodeList arguments,
       CallStructure callStructure,
       A arg);
+
+  /// Access of library through a deferred [prefix].
+  ///
+  /// For instance
+  ///   import 'lib.dart' deferred as prefix;
+  ///
+  ///   m() => prefix.foo;
+  ///
+  /// This visit method is special in that it is called as a pre-step to calling
+  /// the visit method for the actual access. Therefore this method cannot
+  /// return a result to its caller.
+  void previsitDeferredAccess(
+      Send node,
+      PrefixElement prefix,
+      A arg);
 }
 
 abstract class SemanticDeclarationVisitor<R, A> {
   R apply(Node node, A arg);
 
   /// Apply this visitor to the [parameters].
   applyParameters(NodeList parameters, A arg);
 
   /// Apply this visitor to the initializers of [constructor].
   applyInitializers(FunctionExpression constructor, A arg);
@@ skipping 551 matching lines @@
   ///       C() : this._(42);
   ///     }
   ///
   R errorUnresolvedThisConstructorInvoke(
       Send node,
       Element element,
       NodeList arguments,
       Selector selector,
       A arg);
 }