| Index: sdk/lib/_internal/compiler/implementation/typechecker.dart | 
| =================================================================== | 
| --- sdk/lib/_internal/compiler/implementation/typechecker.dart	(revision 15242) | 
| +++ sdk/lib/_internal/compiler/implementation/typechecker.dart	(working copy) | 
| @@ -154,8 +154,10 @@ | 
| final Element element; | 
| final Link<DartType> arguments; | 
|  | 
| -  const InterfaceType(this.element, | 
| -                      [this.arguments = const Link<DartType>()]); | 
| +  InterfaceType(this.element, | 
| +                [this.arguments = const Link<DartType>()]) { | 
| +    assert(invariant(element, element.isDeclaration)); | 
| +  } | 
|  | 
| TypeKind get kind => TypeKind.INTERFACE; | 
|  | 
|  |