Look up the correct constructor for default classes.

lib/compiler/implementation/elements/elements.dart

Index: lib/compiler/implementation/elements/elements.dart
diff --git a/lib/compiler/implementation/elements/elements.dart b/lib/compiler/implementation/elements/elements.dart
index c1da9dc56336a3824608c1280028f9d14e37012b..a80e63a7460de4a2507ae0d2364bdd1cd61434ea 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -825,6 +825,20 @@ class ClassElement extends ContainerElement {
     forEachMember(fieldFilter, includeBackendMembers, includeSuperMembers);
   }
 
+  bool implementsInterface(ClassElement intrface) {
+    assert(intrface.isInterface());

[ahe, 2012/04/10 14:30:38]

I don't think this assertion is correct. We have implicit interfaces from a
class declaration.

[floitsch, 2012/04/11 11:40:56]

Done.

+    if (allSupertypes === null) {

[ahe, 2012/04/10 14:30:38]

I don't understand why this is better than a null pointer exception in for-in
below. The user doesn't care: the compiler crashed and did not give her any
usable information for trying to locate the problem.

[floitsch, 2012/04/11 11:40:56]

removed.

+      throw "internal error: implementsInterface with allSupertypes == null.";      

[ahe, 2012/04/10 14:30:38]

Long line: trailing whitespace?

[floitsch, 2012/04/11 11:40:56]

removed.

+    }
+    for (Type implementedInterfaceType in allSupertypes) {
+      ClassElement implementedInterface = implementedInterfaceType.element;
+      if (implementedInterface == intrface) {

[ahe, 2012/04/10 14:30:38]

Use ===, not ==.

[floitsch, 2012/04/11 11:40:56]

Done.

+        return true;
+      }
+    }
+    return false;
+  }
+
   bool isInterface() => false;
   bool isNative() => nativeName != null;
   SourceString nativeName;