Be smarter about when disabling tree-shaking.

dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.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.
 
 part of js_backend;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked;
 
   JavaScriptItemCompilationContext()
@@ skipping 57 matching lines @@
 
   Element getInterceptorMethod;
   Element interceptedNames;
 
   HType stringType;
   HType indexablePrimitiveType;
   HType readableArrayType;
   HType mutableArrayType;
   HType fixedArrayType;
   HType extendableArrayType;
-  
 
   // TODO(9577): Make it so that these are not needed when there are no native
   // classes.
   Element dispatchPropertyName;
   Element getNativeInterceptorMethod;
   Element defineNativeMethodsFinishMethod;
   Element getDispatchPropertyMethod;
   Element setDispatchPropertyMethod;
   Element initializeDispatchPropertyMethod;
   bool needToInitializeDispatchProperty = false;
@@ skipping 60 matching lines @@
    * Set of classes whose `operator ==` methods handle `null` themselves.
    */
   final Set<ClassElement> specialOperatorEqClasses = new Set<ClassElement>();
 
   List<CompilerTask> get tasks {
     return <CompilerTask>[builder, optimizer, generator, emitter];
   }
 
   final RuntimeTypes rti;
 
+  /// Holds the method "disableTreeShaking" in js_mirrors when
+  /// dart:mirrors has been loaded.
+  FunctionElement disableTreeShakingMarker;
+
+  /// Holds the method "preserveNames" in js_mirrors when
+  /// dart:mirrors has been loaded.
+  FunctionElement preserveNamesMarker;
+
   JavaScriptBackend(Compiler compiler, bool generateSourceMap, bool disableEval)
       : namer = determineNamer(compiler),
         usedInterceptors = new Set<Selector>(),
         oneShotInterceptors = new Map<String, Selector>(),
         interceptedElements = new Map<SourceString, Set<Element>>(),
         rti = new RuntimeTypes(compiler),
         specializedGetInterceptors = new Map<String, Set<ClassElement>>(),
         super(compiler, JAVA_SCRIPT_CONSTANT_SYSTEM) {
     emitter = disableEval
         ? new CodeEmitterNoEvalTask(compiler, namer, generateSourceMap)
@@ skipping 938 matching lines @@
   ClassElement get stringImplementation => jsStringClass;
   ClassElement get listImplementation => jsArrayClass;
   ClassElement get constListImplementation => jsArrayClass;
   ClassElement get fixedListImplementation => jsFixedArrayClass;
   ClassElement get growableListImplementation => jsExtendableArrayClass;
   ClassElement get mapImplementation => mapLiteralClass;
   ClassElement get constMapImplementation => constMapLiteralClass;
   ClassElement get typeImplementation => typeLiteralClass;
   ClassElement get boolImplementation => jsBoolClass;
   ClassElement get nullImplementation => jsNullClass;
+
+  void enableMirrors() {
+    LibraryElement library = compiler.libraries['dart:_js_mirrors'];
+    disableTreeShakingMarker =
+        library.find(const SourceString('disableTreeShaking'));
+    preserveNamesMarker =
+        library.find(const SourceString('preserveNames'));
+ }
+
+  void registerStaticUse(Element element, Enqueuer enqueuer) {
+    if (element == disableTreeShakingMarker) {
+      enqueuer.enqueueEverything();
+    } else if (element == preserveNamesMarker) {
+    }

[Johnni Winther, 2013/06/13 07:08:29]

Something missing in this block?

[ahe, 2013/06/14 12:00:22]

Yes.  I'll fill in more stuff in future CLs.

+  }
 }