Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/resolution/members.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 resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(Node node);
@@ skipping 2432 matching lines @@
     if (type == null) return null;
     if (inCheckContext) {
       compiler.enqueuer.resolution.registerIsCheck(type);
     }
     if (typeRequired || inCheckContext) {
       if (type is InterfaceType) {
         InterfaceType itf = type;
         itf.typeArguments.forEach((DartType argument) {
           analyzeTypeArgument(type, argument);
         });
+      } else if (type is TypeVariableType) {
+        ClassElement currentClass = enclosingElement.getEnclosingClass();

[ahe, 2013/02/14 16:58:33]

I think this is shadowing a field (which contains the same value).

[karlklose, 2013/02/18 16:02:01]

Done, removed.

+        compiler.world.registerTypeVariableCheck(currentClass);

[ngeoffray, 2013/02/18 09:27:58]

Register in resolver world?

[karlklose, 2013/02/18 16:02:01]

Why? This is done to add the class to the set of classes needing rti and to note
the fact that it uses its argument in a check.  The is-check is already
registered in l. 2445 above.

[ngeoffray, 2013/02/19 09:00:41]

If codegen doesn't need to know what classes make type variable check, I would
not register it. If emitter requires to know, I would have the codegen register
it in the codegen's world.

The "global" world is something we'll try to rip off a bit, and it should not
contain backend specific things. Collecting the classes that do type variable
check is required just because of the JS backend. So actually, this is something
the codegen should register to the js_backend.

[karlklose, 2013/02/19 12:39:28]

I moved this set to the backend.

       }
-      // TODO(ngeoffray): Also handle cases like:
-      // 1) a is T
-      // 2) T a (in checked mode).
+      // TODO(ngeoffray): Also handle T a (in checked mode).
     }
     return type;
   }
 
   visitModifiers(Modifiers node) {
     // TODO(ngeoffray): Implement this.
     unimplemented(node, 'modifiers');
   }
 
   visitLiteralList(LiteralList node) {
@@ skipping 1190 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }