Do not create placeholders for elements that won't be later renamed.

lib/compiler/implementation/dart_backend/placeholder_collector.dart

 // 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 LocalPlaceholder implements Hashable {
   final String identifier;
   final Set<Node> nodes;
   LocalPlaceholder(this.identifier) : nodes = new Set<Node>();
   int hashCode() => identifier.hashCode();
   String toString() =>
@@ skipping 80 matching lines @@
   final Compiler compiler;
   final Set<Node> nullNodes;  // Nodes that should not be in output.
   final Set<Identifier> unresolvedNodes;
   final Map<Element, Set<Node>> elementNodes;
   final Map<FunctionElement, Set<LocalPlaceholder>> localPlaceholders;
   final Map<LibraryElement, Set<Identifier>> privateNodes;
   Map<String, LocalPlaceholder> currentLocalPlaceholders;
   Element currentElement;
   TreeElements treeElements;
 
+  LibraryElement get coreLibrary => compiler.coreLibrary;
+  FunctionElement get entryFunction => compiler.mainApp.find(Compiler.MAIN);
+
   PlaceholderCollector(this.compiler) :
       nullNodes = new Set<Node>(),
       unresolvedNodes = new Set<Identifier>(),
       elementNodes = new Map<Element, Set<Node>>(),
       localPlaceholders = new Map<FunctionElement, Set<LocalPlaceholder>>(),
       privateNodes = new Map<LibraryElement, Set<Identifier>>();
 
   void collectFunctionDeclarationPlaceholders(
       FunctionElement element, FunctionExpression node) {
     if (element.isGenerativeConstructor() || element.isFactoryConstructor()) {
@@ skipping 139 matching lines @@
     makeElementPlaceholder(node, type.element);
   }
 
   void makeNullPlaceholder(Node node) {
     assert(node is Identifier || node is Send);
     nullNodes.add(node);
   }
 
   void makeElementPlaceholder(Node node, Element element) {
     assert(element !== null);
+    if (element === entryFunction) return;

[Roman, 2012/08/21 07:44:58]

This is not the problem of your CL, but we should actually have an element for
MAIN, because otherwise another library may define it's own main element that
won't be renamed:

#library('lib.dart');
void main() {}

...
#import('lib.dart', prefix:'lib');
main() {
  lib.main();
}

To fix this, we should check MAIN element in rename and don't rename it, but
instead just add it to used top level identifiers. OR we can just add 'main' to
used top level identifiers in renamer at the beginning.

[Anton Muhin, 2012/08/21 09:16:54]

Good point, I'll fix it.

On 2012/08/21 07:44:58, Roman wrote:

+    if (element.getLibrary() === coreLibrary) return;
     elementNodes.putIfAbsent(element, () => new Set<Node>()).add(node);
   }
 
   void makePrivateIdentifier(Identifier node) {
     assert(node !== null);
     privateNodes.putIfAbsent(
         currentElement.getLibrary(), () => new Set<Identifier>()).add(node);
   }
 
   void makeUnresolvedPlaceholder(Node node) {
@@ skipping 153 matching lines @@
       visit(node.defaultClause.typeArguments);
     }
   }
 
   visitTypedef(Typedef node) {
     assert(currentElement is TypedefElement);
     makeElementPlaceholder(node.name, currentElement);
     node.visitChildren(this);
   }
 }