Introduce AST cloning.

lib/compiler/implementation/dart_backend/placeholder_collector.dart

Index: lib/compiler/implementation/dart_backend/placeholder_collector.dart
diff --git a/lib/compiler/implementation/dart_backend/placeholder_collector.dart b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
index 39130b0952d8e7c7ca934da43b795ed581e4ed3c..b0131c6890f591261de77574054e448e0bbd7f52 100644
--- a/lib/compiler/implementation/dart_backend/placeholder_collector.dart
+++ b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
@@ -133,6 +133,7 @@ class SendVisitor extends ResolvedVisitor {
 class PlaceholderCollector extends AbstractVisitor {
   final Compiler compiler;
   final Set<String> fixedMemberNames; // member names which cannot be renamed.
+  final Map<Element, ElementAst> elementAsts;
   final Set<Node> nullNodes;  // Nodes that should not be in output.
   final Set<Identifier> unresolvedNodes;
   final Map<Element, Set<Node>> elementNodes;
@@ -147,7 +148,7 @@ class PlaceholderCollector extends AbstractVisitor {
   LibraryElement get coreLibrary => compiler.coreLibrary;
   FunctionElement get entryFunction => compiler.mainApp.find(Compiler.MAIN);
 
-  PlaceholderCollector(this.compiler, this.fixedMemberNames) :
+  PlaceholderCollector(this.compiler, this.fixedMemberNames, this.elementAsts) :
       nullNodes = new Set<Node>(),
       unresolvedNodes = new Set<Identifier>(),
       elementNodes = new Map<Element, Set<Node>>(),
@@ -197,8 +198,11 @@ class PlaceholderCollector extends AbstractVisitor {
       if (element.defaultImplementation !== null
           && element.defaultImplementation !== element) {
         FunctionElement implementingFactory = element.defaultImplementation;
-        tryMakeConstructorNamePlaceholder(implementingFactory.cachedNode,
-            element.getEnclosingClass());
+        if (implementingFactory is !SynthesizedConstructorElement) {

[Roman, 2012/09/07 08:10:56]

Why this check? If it fixes something, please add a test (or better fix it in a
separate CL). I also remember there was a CL that changed something in
shouldOutput about SynthesizedConstructorElement, is it related?

[Anton Muhin, 2012/09/07 12:26:07]

This is somewhat related as we started to drop synthesize constructors earlier.

On the other hand, there is no need to create a placeholder for them anyway as
they won't get output.

If you like I can fix it differently by building AST even for synthesize ctors
and move discarding them back to emitter, but I am not sure it's really better.

On 2012/09/07 08:10:56, Roman wrote:

+          tryMakeConstructorNamePlaceholder(
+              elementAsts[implementingFactory].ast,
+              element.getEnclosingClass());
+        }
       }
     } else if (Elements.isStaticOrTopLevel(element)) {
       // Note: this code should only rename private identifiers for class'
@@ -224,16 +228,17 @@ class PlaceholderCollector extends AbstractVisitor {
     }
   }
 
-  void collect(Element element, TreeElements elements) {
-    treeElements = elements;
-    currentElement = element;
-    Node elementNode = currentElement.parseNode(compiler);
+  void collect(Element element) {
+    this.currentElement = element;
+    final ElementAst elementAst = elementAsts[element];
+    this.treeElements = elementAst.treeElements;
+    Node elementNode = elementAst.ast;
     if (element is FunctionElement) {
       collectFunctionDeclarationPlaceholders(element, elementNode);
     } else if (element is VariableListElement) {
       VariableDefinitions definitions = elementNode;
       for (Node definition in definitions.definitions) {
-        final definitionElement = elements[definition];
+        final definitionElement = treeElements[definition];
         // definitionElement === null if variable is actually unused.
         if (definitionElement === null) continue;
         collectFieldDeclarationPlaceholders(definitionElement, definition);