Ensure locations are always provided, but don't store them yet.

pkg/front_end/lib/src/fasta/builder/class_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.class_builder;
 
 import 'builder.dart' show
     Builder,
     ConstructorReferenceBuilder,
     LibraryBuilder,
@@ skipping 12 matching lines @@
 
   T supertype;
 
   List<T> interfaces;
 
   final Map<String, Builder> members;
 
   ClassBuilder(
       List<MetadataBuilder> metadata, int modifiers,
       String name, this.typeVariables, this.supertype, this.interfaces,
-      this.members, List<T> types, LibraryBuilder parent)
-      : super(metadata, modifiers, name, types, parent);
+      this.members, List<T> types, LibraryBuilder parent, int charOffset)
+      : super(metadata, modifiers, name, types, parent, charOffset);
 
   List<ConstructorReferenceBuilder> get constructorReferences => null;
 
   Map<String, Builder> get constructors;
 
   Map<String, Builder> get membersInScope => members;
 
   int resolveTypes(LibraryBuilder library) {
     Scope scope;
     int count = 0;
@@ skipping 21 matching lines @@
       Map<String, Builder> local = <String, Builder>{};
       for (TypeVariableBuilder t in typeVariables) {
         local[t.name] = t;
       }
       parent = new Scope(local, parent, isModifiable: false);
     }
     return new Scope(membersInScope, parent, isModifiable: false);
   }
 
   /// Used to lookup a static member of this class.
-  Builder findStaticBuilder(String name, {bool isSetter: false}) {
+  Builder findStaticBuilder(String name, int charOffset, Uri fileUri,
+      {bool isSetter: false}) {
     Builder builder = members[name];
     if (builder?.next != null) {
       Builder getterBuilder;
       Builder setterBuilder;
       Builder current = builder;
       while (current != null) {
         if (current.isGetter && getterBuilder == null) {
           getterBuilder = current;
         } else if (current.isSetter && setterBuilder == null) {
           setterBuilder = current;
         } else {
-          return new AmbiguousBuilder(builder);
+          return new AmbiguousBuilder(builder, charOffset, fileUri);
         }
         current = current.next;
       }
       builder = isSetter ? setterBuilder : getterBuilder;
     }
     if (builder == null) {
       return null;
     } else if (isSetter && builder.isGetter) {
       return null;
     } else {
       return builder.isInstanceMember ? null : builder;
     }
   }
 
   Builder findConstructorOrFactory(String name);
 }