Fix analyzer warnings in assertions of the TypeExpression CL

pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index cee53f052876776ae71e03e0dfc89643ac841113..e73dd846c674e07c154c69781fc54ade0d53c937 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -1865,7 +1865,7 @@ class TypeExpression extends Primitive {
                  List<Primitive> arguments)
       : this.arguments = _referenceList(arguments) {
     assert(kind == TypeExpressionKind.INSTANCE
-           ? dartType == dartType.element.thisType
+           ? dartType == (dartType.element as ClassElement).thisType
            : true);
   }