Implement dynamic function checks.

dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
index 97caf52b04124bd7f54d3afb0f7c03ba51af2b8e..5067c2870c58cb727a6f292edd32c7c3b180c34c 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
@@ -47,6 +47,8 @@ class ClassEmitter extends CodeEmitterHelper {
       additionalProperties.forEach(builder.addProperty);
     }
 
+    emitTypeVariableReaders(classElement, builder);
+
     emitClassBuilderWithReflectionData(
         className, classElement, builder, properties);
   }
@@ -563,4 +565,46 @@ class ClassEmitter extends CodeEmitterHelper {
       builder.addProperty('+$reflectionName', reflectable);
     }
   }
+
+  void emitTypeVariableReaders(ClassElement cls, ClassBuilder builder) {
+    List typeVariables = [];
+    ClassElement superclass = cls;
+    while (superclass != null) {
+      GenericType type = superclass.thisType;
+      for (TypeVariableType parameter in type.typeArguments) {

[Johnni Winther, 2013/12/03 10:33:16]

Replace `type.typeArguments` with `superclass.typeVariables` and delete the
`type` variable.

[ahe, 2013/12/05 14:24:23]

Done.

+        if (task.readTypeVariables.contains(parameter.element)) {
+          emitTypeVariableReader(cls, builder, parameter.element);
+        }
+      }
+      superclass = superclass.superclass;
+    }
+  }
+
+  void emitTypeVariableReader(ClassElement cls,
+                              ClassBuilder builder,
+                              TypeVariableElement element) {
+    String name = namer.readTypeVariableName(element);
+    jsAst.Expression index =
+        js.toExpression(RuntimeTypes.getTypeVariableIndex(element));
+    jsAst.Expression computeTypeVariable;
+
+    Substitution substitution =
+        backend.rti.computeSubstitution(
+            cls, element.enclosingElement, alwaysGenerateFunction: true);
+    if (substitution != null) {
+      jsAst.Expression typeArguments =
+          substitution.getCode(backend.rti, true)['apply'](

[Johnni Winther, 2013/12/03 10:33:16]

Seems the last argument to getCode should be named. I cannot locally see what
`true` means.

[ahe, 2013/12/05 14:24:23]

I like to avoid adding named arguments as they add extra overhead at runtime,
and because they have a tendency to be followed by more.

+              ['null', r'this.$builtinTypeInfo']);
+      computeTypeVariable = typeArguments[index];
+    } else {
+      // TODO(ahe): These can be generated dynamically.
+      computeTypeVariable =
+          js(r'this.$builtinTypeInfo && this.$builtinTypeInfo[#]', index);
+    }
+    jsAst.Expression convertRtiToRuntimeType =
+        namer.elementAccess(compiler.findHelper('convertRtiToRuntimeType'));
+    builder.addProperty(
+        name, js.fun(
+            [], [js.return_(convertRtiToRuntimeType(computeTypeVariable))]));
+  }
 }