Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/world.dart

Index: sdk/lib/_internal/compiler/implementation/world.dart
diff --git a/sdk/lib/_internal/compiler/implementation/world.dart b/sdk/lib/_internal/compiler/implementation/world.dart
index 19a3aaf757cecdb65455ff73478e8402870a823d..7bd6ee22afb0c1256fe05da7613d6579504973c9 100644
--- a/sdk/lib/_internal/compiler/implementation/world.dart
+++ b/sdk/lib/_internal/compiler/implementation/world.dart
@@ -79,12 +79,31 @@ class World {
       }
     }
 
+    Set<ClassElement> classesUsingTypeVariableTests = new Set<ClassElement>();
     compiler.resolverWorld.isChecks.forEach((DartType type) {
-      if (type is InterfaceType) {
+      if (type.kind == TypeKind.TYPE_VARIABLE) {
+        TypeVariableElement variable = type.element;
+        classesUsingTypeVariableTests.add(variable.enclosingElement);
+      }
+    });
+    // Add is-checks that result from classes using type variables in checks.
+    compiler.resolverWorld.addImplicitChecks(classesUsingTypeVariableTests);
+    // Add the rti dependencies that are implicit in the way the backend
+    // generates code: when we create a new [List], we actually create
+    // a JSArray in the backend and we need to add type arguments to
+    // the calls of the list constructor whenever we determine that
+    // JSArray needs type arguments.
+    compiler.backend.addBackendRtiDependencies(this);
+    // Compute the set of all classes that need runtime type information.
+    compiler.resolverWorld.isChecks.forEach((DartType type) {
+      if (type.kind == TypeKind.INTERFACE) {
         InterfaceType itf = type;
         if (!itf.isRaw) {
           potentiallyAddForRti(itf.element);
         }
+      } else if (type.kind == TypeKind.TYPE_VARIABLE) {
+        TypeVariableElement variable = type.element;
+        potentiallyAddForRti(variable.enclosingElement);
       }
     });
   }
@@ -102,7 +121,6 @@ class World {
     return uses != null && !uses.isEmpty;
   }
 
-
   void registerRtiDependency(Element element, Element dependency) {
     // We're not dealing with typedef for now.
     if (!element.isClass() || !dependency.isClass()) return;