Handle complicated imports.

pkg/front_end/lib/src/fasta/builder/library_builder.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 fasta.library_builder;
 
 import '../combinator.dart' show Combinator;
 
 import '../errors.dart' show InputError, internalError, printUnexpected;
 
@@ skipping 68 matching lines @@
   void addNit(int charOffset, Object message,
       {Uri fileUri, bool silent: false}) {
     fileUri ??= this.fileUri;
     if (!silent) {
       nit(fileUri, charOffset, message);
     }
   }
 
   bool addToExportScope(String name, Builder member);
 
-  void addToScope(String name, Builder member);
+  void addToScope(String name, Builder member, int charOffset, bool isImport);
 
   Builder buildAmbiguousBuilder(
-      String name, Builder builder, Builder other, int charOffset);
+      String name, Builder builder, Builder other, int charOffset,
+      {bool isExport: false, bool isImport: false});
 
   int finishStaticInvocations() => 0;
 
   int finishNativeMethods() => 0;
 
   /// Looks up [constructorName] in the class named [className]. It's an error
   /// if no such class is exported by this library, or if the class doesn't
   /// have a matching constructor (or factory).
   ///
   /// If [constructorName] is null or the empty string, it's assumed to be an
@@ skipping 21 matching lines @@
   }
 
   int finishTypeVariables(ClassBuilder object) => 0;
 
   void becomeCoreLibrary(dynamicType, voidType) {
     addBuilder("dynamic",
         new DynamicTypeBuilder<T, dynamic>(dynamicType, this, -1), -1);
     addBuilder("void", new VoidTypeBuilder<T, dynamic>(voidType, this, -1), -1);
   }
 }