Throw when reflecting on elements not covered by a `MirrorsUsed` annotation.

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 1516 matching lines @@
           targetsUsed.add(field.getter);
           targetsUsed.add(field.setter);
         } else {
           targetsUsed.add(target);
         }
       }
     }
     if (metaTargets != null) metaTargetsUsed.addAll(metaTargets);
   }
 
+  /// Returns `true` if [element] can be accessed through reflection, that is,
+  /// is in the set of elements covered by a `MirrorsUsed` annotation.
+  bool isAccessibleByReflection(Element element) {

[ahe, 2013/08/26 20:41:15]

I'm not sure this method is different from isNeededForReflection.

However, it could be a problem that this returns true when
hasInsufficientMirrorsUsed.

The problem is that "isTreeShakingDisabled" means: someone is using reflection
to invoke methods. (Or actually, if isTreeShakingDisabled is false, no methods
are invoked reflectively).

This is important as dart:mirrors may be imported to access
MirrorSystem.getName. But that shouldn't change how methods are generated.

+    if (hasInsufficientMirrorsUsed) return true;
+    return isNeededForReflection(element);
+  }
+
   bool isNeededForReflection(Element element) {
     if (hasInsufficientMirrorsUsed) return isTreeShakingDisabled;
     /// Record the name of [element] in [symbolsUsed]. Return true for
     /// convenience.
     bool registerNameOf(Element element) {
       symbolsUsed.add(element.name.slowToString());
       if (element.isConstructor()) {
         symbolsUsed.add(element.getEnclosingClass().name.slowToString());
       }
       return true;
@@ skipping 74 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }