Implement subtype checks on type arguments.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 7b7df7049c2abed7692025b1268dc227ab6a7322..71e618f7e7c7f0b2078763eb95e3dfa66d5dc97c 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -63,6 +63,11 @@ class CodeEmitterTask extends CompilerTask {
 
   final bool generateSourceMap;
 
+  RuntimeTypeInformation get rti {

[ngeoffray, 2012/12/12 12:09:11]

I'd rather not have this getter.

[karlklose, 2012/12/12 14:50:47]

Done.

+    JavaScriptBackend backend = compiler.backend;
+    return backend.rti;
+  }
+
   CodeEmitterTask(Compiler compiler, Namer namer, this.generateSourceMap)
       : boundClosureBuffer = new CodeBuffer(),
         mainBuffer = new CodeBuffer(),
@@ -753,6 +758,33 @@ $lazyInitializerLogic
     }
   }
 
+  void emitRuntimeClassesAndTests(CodeBuffer buffer) {
+    TypeChecks typeChecks = rti.computeRequiredChecks();
+    // Create an object that holds the class name and the checks for all classes
+    // that are needed but do  not have a JS constructor.

[ngeoffray, 2012/12/12 12:09:11]

do  not -> do not

[ngeoffray, 2012/12/12 12:09:11]

What are those? Please add a comment.

[karlklose, 2012/12/12 14:50:47]

Done.

[karlklose, 2012/12/12 14:50:47]

Done.

+    for (ClassElement requiredClass in rti.requiredClasses) {
+      String holder = namer.isolateAccess(requiredClass);
+      String name = namer.getName(requiredClass);
+      buffer.add("$holder = {builtin\$cls: '$name'");
+      typeChecks[requiredClass].forEach((check) {
+        buffer.add(', is\$${namer.getName(check)}: true');
+      });
+      buffer.add('};\n');
+    }
+    // Add checks to the constructors of instantiated classes.
+    for (ClassElement cls in typeChecks) {
+      if (rti.requiredClasses.contains(cls)) {
+        // We already emitted the is-checks in the object definition for this
+        // class.
+        continue;
+      }
+      String holder = namer.isolateAccess(cls);
+      typeChecks[cls].forEach((check) {
+        buffer.add('$holder.is\$${namer.getName(check)} = true;\n');
+      });
+    }
+  }
+
   /**
    * Documentation wanted -- johnniwinther
    *
@@ -1918,6 +1950,7 @@ if (typeof document !== 'undefined' && document.readyState !== 'complete') {
       // We need to finish the classes before we construct compile time
       // constants.
       emitFinishClassesInvocationIfNecessary(mainBuffer);
+      emitRuntimeClassesAndTests(mainBuffer);
       emitCompileTimeConstants(mainBuffer);
       // Static field initializations require the classes and compile-time
       // constants to be set up.