Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart b/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
index bfad2078dfcb9b3a5fea2f08d9412d4320bf9230..e8930755916d4ea7b4d2dfa521bf0b4067a46537 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.dart
@@ -62,6 +62,16 @@ class RuntimeTypeInformation {
         }
       }
     }
+
+    // TODO(karlklose): remove this temporary fix: we need to add the classes
+    // used in substitutions to addArguments.

[ngeoffray, 2013/02/28 12:14:52]

What's the implication of this? The comment is not very helping describing the
problem.

[karlklose, 2013/02/28 12:20:46]

We will generate holders for these in every program.

[ngeoffray, 2013/02/28 12:39:03]

OK, please make sure fixing this is #1 in your TODO list, to keep hello world
tidy.

+    allArguments.addAll([compiler.intClass,
+                         compiler.boolClass,
+                         compiler.numClass,
+                         compiler.doubleClass,
+                         compiler.stringClass,
+                         compiler.listClass]);
+
     return cachedRequiredChecks = requiredChecks;
   }
 
@@ -294,4 +304,14 @@ class TypeCheckMapping implements TypeChecks {
   }
 
   Iterator<ClassElement> get iterator => map.keys.iterator;
+
+  String toString() {
+    StringBuffer sb = new StringBuffer();
+    for (ClassElement holder in this) {
+      for (ClassElement check in [holder]) {
+        sb.add('${holder.name.slowToString()}.${check.name.slowToString()}, ');
+      }
+    }
+    return '[$sb]';
+  }
 }