Implement is-checks against type variables.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index 3bc06c91da6a14d4f45bf466365ad3a304afe449..54ffa9b681b67f8a799b906c8879f1af24891162 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -662,6 +662,17 @@ class JavaScriptBackend extends Backend {
 
   final Map<Element, ReturnInfo> returnInfo;
 
+  Iterable<ClassElement> cachedClassesUsingTypeVariableTests;

[ngeoffray, 2013/02/21 10:26:18]

Should that be in the emitter instead? It would like very dangerous to call it
before we are done compiling methods.

[karlklose, 2013/02/21 14:48:44]

Done.

+
+  Iterable<ClassElement> get classesUsingTypeVariableTests {
+    if (cachedClassesUsingTypeVariableTests == null) {
+      cachedClassesUsingTypeVariableTests = rti.isChecks
+          .where((DartType t) => t is TypeVariableType)
+          .map((TypeVariableType v) => v.element.getEnclosingClass());
+    }
+    return cachedClassesUsingTypeVariableTests;
+  }
+
   /**
    * Documentation wanted -- johnniwinther
    *
@@ -995,11 +1006,12 @@ class JavaScriptBackend extends Backend {
   }
 
   void registerIsCheck(DartType type, Enqueuer world) {
-    if (!type.isRaw) {
+    if (!type.isRaw || type is TypeVariableType) {

[ngeoffray, 2013/02/21 10:26:18]

use type.kind instead?

[karlklose, 2013/02/21 14:48:44]

Done.

       enqueueInResolution(getSetRuntimeTypeInfo());
       enqueueInResolution(getGetRuntimeTypeInfo());
       enqueueInResolution(getGetRuntimeTypeArgument());
       enqueueInResolution(getCheckArguments());
+      enqueueInResolution(getGetObjectIsSubtype());

[ngeoffray, 2013/02/21 10:26:18]

Isn't that one just requires by TypeVariableType?

[karlklose, 2013/02/21 14:48:44]

Done.

     }
     // [registerIsCheck] is also called for checked mode checks, so we
     // need to register checked mode helpers.
@@ -1444,6 +1456,10 @@ class JavaScriptBackend extends Backend {
     return compiler.findHelper(const SourceString('checkArguments'));
   }
 
+  Element getGetObjectIsSubtype() {
+    return compiler.findHelper(const SourceString('objectIsSubtype'));
+  }
+
   Element getThrowNoSuchMethod() {
     return compiler.findHelper(const SourceString('throwNoSuchMethod'));
   }