RFC: Resolution based tree-shaking.

dart/lib/compiler/implementation/compiler.dart

Index: dart/lib/compiler/implementation/compiler.dart
diff --git a/dart/lib/compiler/implementation/compiler.dart b/dart/lib/compiler/implementation/compiler.dart
index 2b4679c73003466009e44e4fbf641bcc0d964b2b..755d053a379d863723d88a6de467ecf5347cafed 100644
--- a/dart/lib/compiler/implementation/compiler.dart
+++ b/dart/lib/compiler/implementation/compiler.dart
@@ -15,7 +15,17 @@ class WorkItem {
   String run(Compiler compiler, Enqueuer world) {
     String code = world.universe.generatedCode[element];
     if (code !== null) return code;
-    if (!isAnalyzed()) compiler.analyze(this);
+    if (!isAnalyzed()) {
+      resolutionTree = world.getCachedElements(element);

[kasperl, 2012/06/12 05:50:12]

So getCachedElements has the side-effect that this work item might turn
analyzed?

[ahe, 2012/06/12 06:22:48]

getCachedElements does not have side-effects. Assigning to treeElements has the
effect that this work item may "become" analyzed. 

+      if (!isAnalyzed()) compiler.analyze(this);
+    }
+    if (world.isFirstQueue) {
+      world.resolvedElements[element] = resolutionTree;
+      return null;
+    }
+    if (resolutionTree === null) {
+      compiler.internalError('Error: unresolved element', element: element);
+    }
     return compiler.codegen(this);
   }
 }
@@ -366,31 +376,40 @@ class Compiler implements DiagnosticListener {
     // should know this.
     world.populate(this, libraries.getValues());
 
-    // Not yet ready to process the enqueuer.resolution queue...
-    // processQueue(enqueuer.resolution);
+    log('Resolving');
+    processQueue(enqueuer.resolution, main);
+    log('Resolved ${enqueuer.resolution.resolvedElements.length} elements.');
+
+    log('Compiling');
     processQueue(enqueuer.codegen, main);
 
     backend.assembleProgram();
-    if (!enqueuer.codegen.queue.isEmpty()) {
-      internalErrorOnElement(enqueuer.codegen.queue.first().element,
-                             "work list is not empty");
-    }
+    enqueuer.codegen.forEach((WorkItem work) {
+      internalErrorOnElement(work.element, "work list is not empty");
+    });
   }
 
   processQueue(Enqueuer world, Element main) {
     backend.processNativeClasses(world, libraries.getValues());
     world.addToWorkList(main);
     codegenProgress.reset();
-    while (!world.queue.isEmpty()) {
-      WorkItem work = world.queue.removeLast();
+    world.forEach((WorkItem work) {
       withCurrentElement(work.element, () => work.run(this, world));
-    }
+    });
     world.queueIsClosed = true;
     assert(world.checkNoEnqueuedInvokedInstanceMethods());
     world.registerFieldClosureInvocations();
   }
 
   TreeElements analyzeElement(Element element) {
+    if (element is AbstractFieldElement) {
+      return null;
+    }
+    final int allowed = ElementCategory.VARIABLE | ElementCategory.FUNCTION
+                        | ElementCategory.FACTORY;
+    if (!element.isAccessor() && (element.kind.category & allowed) == 0) {
+      return null;
+    }
     assert(parser !== null);
     Node tree = parser.parse(element);
     validator.validate(tree);
@@ -509,11 +528,16 @@ class Compiler implements DiagnosticListener {
       element = currentElement;
     }
     Token position = element.position();
+    Uri uri = element.getCompilationUnit().script.uri;
     if (position === null) {
-      Uri uri = element.getCompilationUnit().script.uri;
       return new SourceSpan(uri, 0, 0);
+    } else {
+      return SourceSpan.withOffsets(
+          position, position,
+          (beginOffset, endOffset) {
+            return new SourceSpan(uri, beginOffset, endOffset);
+          });
     }
-    return spanFromTokens(position, position);
   }
 
   Script readScript(Uri uri, [ScriptTag node]) {