Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index c13a959fba023648db53175a4c61313727423049..466ae9415a17ce560ac33b81dfc85821bf31e1d0 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -2450,10 +2450,11 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
         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;
   }