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

pkg/front_end/lib/src/fasta/dill/dill_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.dill_library_builder;
 
 import 'package:kernel/ast.dart' show
     Class,
     ExpressionStatement,
     Field,
@@ skipping 31 matching lines @@
 
   final Map<String, Builder> members = <String, Builder>{};
 
   // TODO(ahe): Some export information needs to be serialized.
   final Map<String, Builder> exports = <String, Builder>{};
 
   final DillLoader loader;
 
   Library library;
 
-  DillLibraryBuilder(this.uri, this.loader);
+  DillLibraryBuilder(Uri uri, this.loader)
+      : uri = uri, super(uri);

[Johnni Winther, 2017/02/13 08:42:03]

Isn't initializing formal also parameters now by default?

[ahe, 2017/02/13 10:44:23]

I don't know. I'd like  to be able to continue performance testing this on a
Dart VM from November.

 
   get scope => internalError("Scope not supported");
 
   Uri get fileUri => uri;
 
   void addClass(Class cls) {
     DillClassBuilder classBulder = new DillClassBuilder(cls, this);
     addBuilder(cls.name, classBulder);
     cls.procedures.forEach(classBulder.addMember);
     cls.constructors.forEach(classBulder.addMember);
@@ skipping 42 matching lines @@
 
   bool addToExportScope(String name, Builder member) {
     return internalError("Not implemented yet.");
   }
 
   void addToScope(String name, Builder member) {
     internalError("Not implemented yet.");
   }
 
   KernelInvalidTypeBuilder buildAmbiguousBuilder(
-      String name, Builder builder, Builder other) {
-    return new KernelInvalidTypeBuilder(name, this);
+      String name, Builder builder, Builder other, int charOffset) {
+    return new KernelInvalidTypeBuilder(name, charOffset, fileUri);
   }
 }