A visitor that builds a map from node to "Usage".

lib/compiler/implementation/dart_backend/placeholder.dart

Index: lib/compiler/implementation/dart_backend/placeholder.dart
diff --git a/lib/compiler/implementation/dart_backend/placeholder.dart b/lib/compiler/implementation/dart_backend/placeholder.dart
new file mode 100644
index 0000000000000000000000000000000000000000..69f35f65b10b337dff4e17ecdee80933abf5ad52
--- /dev/null
+++ b/lib/compiler/implementation/dart_backend/placeholder.dart
@@ -0,0 +1,27 @@
+// 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.
+
+class Placeholder {
+  abstract String rename(ConflictingRenamer renamer);
+}
+
+class TypePlaceholder extends Placeholder {

[Anton Muhin, 2012/08/08 08:27:20]

looks like all those placeholders can be unified in the simple way: they just
all the elements which should be renamed later.  TypePlaceholder will require
type -> type.element substitution and NullPlaceholder will turn into null
element.

Can it simplify our code and get rid of Placeholder abstraction?

[Roman, 2012/08/09 05:02:35]

Later placeholders will also have scope information, so I would like to keep
them. I can unify method, element and type placeholders at this point.

+  final Type type;
+  TypePlaceholder(this.type);
+  String rename(ConflictingRenamer renamer) =>
+      renamer.renameElement(type.element);
+}

[Anton Muhin, 2012/08/08 08:27:20]

nit: a blank line after class declaration here and below.

[Roman, 2012/08/09 05:02:35]

Done.

+class MethodPlaceholder extends Placeholder {
+  final Element method;
+  MethodPlaceholder(this.method);
+  String rename(ConflictingRenamer renamer) => renamer.renameElement(method);
+}
+class NullPlaceholder extends Placeholder {
+  String rename(ConflictingRenamer renamer) => '';
+}
+class ElementPlaceholder extends Placeholder {
+  final Element element;
+  ElementPlaceholder(this.element);
+  String rename(ConflictingRenamer renamer) => renamer.renameElement(element);
+}