Implement dynamic function checks.

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

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 class ClassEmitter extends CodeEmitterHelper {
   /**
    * Documentation wanted -- johnniwinther
    *
@@ skipping 24 matching lines @@
     }
 
     ClassBuilder builder = new ClassBuilder();
     emitClassConstructor(classElement, builder, runtimeName,
                          onlyForRti: onlyForRti);
     emitFields(classElement, builder, superName, onlyForRti: onlyForRti);
     emitClassGettersSetters(classElement, builder, onlyForRti: onlyForRti);
     emitInstanceMembers(classElement, builder, onlyForRti: onlyForRti);
     task.typeTestEmitter.emitIsTests(classElement, builder);
 
+    emitTypeVariableReaders(classElement, builder);
+
     emitClassBuilderWithReflectionData(
         className, classElement, builder, buffer);
   }
 
   void emitClassConstructor(ClassElement classElement,
                             ClassBuilder builder,
                             String runtimeName,
                             {bool onlyForRti: false}) {
     List<String> fields = <String>[];
     if (!onlyForRti && !classElement.isNative()) {
@@ skipping 539 matching lines @@
     Selector selector = isGetter
         ? new Selector.getter(member.name, member.getLibrary())
         : new Selector.setter(member.name, member.getLibrary());
     String reflectionName = task.getReflectionName(selector, name);
     if (reflectionName != null) {
       var reflectable =
           js(backend.isAccessibleByReflection(member) ? '1' : '0');
       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) {
+        if (task.readTypeVariables.contains(parameter.element)) {
+          emitTypeVariableReader(cls, builder, parameter.element);
+        }
+      }
+      superclass = superclass.superclass;

[Johnni Winther, 2013/10/30 11:40:23]

The superclass chain is not properly substuted. For the hierarchy

class A<T> {}
class B<S> extends A<S> {}
class C<U> extends B<U> {}

you will visit C<U>, B<U>, A<S> if [cls] is C. Use

GenericType type = cls.thisType.asInstanceOf(superclass);

to obtain the correct superclass.

[Johnni Winther, 2013/10/30 12:02:19]

Actually you will visit C<U>, B<S>, A<T> if [cls] is C. Anyway, the fix is the
same.

[ahe, 2013/10/30 12:04:05]

I don't think that is enough.

Consider this situation:

class Foo<T> {
}

class Bar extends Foo<String> {}

What I'm trying to achieve here is to override the method $tv_T in Bar, so that
we get:

Foo.prototype.$tv_T = function() { return /* the value of T */ };

Bar.prototype.$tv_T = function() { return JsString; }

Karl has pointed me to rti.computeSubstitution.

+    }
+  }
+
+  void emitTypeVariableReader(ClassElement cls,
+                              ClassBuilder builder,
+                              TypeVariableElement element) {
+    String name = namer.readTypeVariableName(element);
+    List<jsAst.Node> body;
+    if (cls != element.enclosingElement) {
+      body = <jsAst.Node>[
+          new jsAst.Throw(js.string('Cannot read type variable ${element}'))];

[ahe, 2013/10/29 22:42:49]

This is the only thing that causes tests to fail, and the only two remaining
failures are:

language/function_subtype_bound_closure5_test
language/function_subtype_local5_test

[Johnni Winther, 2013/10/30 11:40:23]

The change above should solve this.

+    } else {
+      body = <jsAst.Node>[
+          js.return_(
+              namer.elementAccess(
+                  compiler.findHelper('convertRtiToRuntimeType'))(
+                      js(r'this.$builtinTypeInfo[#]',
+                         js.toExpression(
+                             RuntimeTypes.getTypeVariableIndex(element)))))];
+    }
+    builder.addProperty(name, js.fun([], body));
+  }
 }