Make TypeMask an interface and start hiding implementation details of FlatTypeMask.

sdk/lib/_internal/compiler/implementation/ssa/codegen.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 ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 1681 matching lines @@
     assignVariable(variableNames.getName(node.receiver), pop());
   }
 
   void registerForeignType(HType type) {
     // TODO(kasperl): This looks shaky. It makes sense if the type is
     // exact, but otherwise we should be registering more types as
     // instantiated. We should find a way of using something along the
     // lines of the NativeEnqueuerBase.processNativeBehavior method.
     if (type.isUnknown()) return;
     TypeMask mask = type.computeMask(compiler);
-    world.registerInstantiatedClass(mask.base.element, work.resolutionTree);
+    world.registerInstantiatedClass(mask.topClass(), work.resolutionTree);

[kasperl, 2013/04/30 14:03:24]

Would exactClass work here?

[ngeoffray, 2013/05/01 12:56:16]

No, so I use containedClasses instead.

   }
 
   visitForeign(HForeign node) {
     String code = node.code.slowToString();
     List<HInstruction> inputs = node.inputs;
     if (node.isJsStatement()) {
       if (!inputs.isEmpty) {
         compiler.internalError("foreign statement with inputs: $code",
                                instruction: node);
       }
@@ skipping 1269 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }