Support checked mode

pkg/compiler/lib/src/resolution/signatures.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.resolution.signatures;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../dart_types.dart';
 import '../elements/elements.dart';
@@ skipping 348 matching lines @@
       LinkBuilder<Element> parametersBuilder =
           visitor.analyzeNodes(formalParameters.nodes);
       requiredParameterCount = parametersBuilder.length;
       parameters = parametersBuilder.toList();
     }
     DartType returnType;
     if (element.isFactoryConstructor) {
       returnType = element.enclosingClass.thisType;
       // Because there is no type annotation for the return type of
       // this element, we explicitly add one.
-      if (compiler.options.enableTypeAssertions) {
-        registry.registerTypeUse(new TypeUse.checkedModeCheck(returnType));
-      }
+      registry.registerTypeUse(new TypeUse.checkedModeCheck(returnType));
     } else {
       AsyncMarker asyncMarker = AsyncMarker.SYNC;
       if (isFunctionExpression) {
         // Use async marker to determine the return type of function
         // expressions.
         FunctionElement function = element;
         asyncMarker = function.asyncMarker;
       }
       switch (asyncMarker) {
         case AsyncMarker.SYNC:
@@ skipping 93 matching lines @@
 /// variables of the function signature itself when its signature is analyzed.
 class FunctionSignatureBuildingScope extends TypeVariablesScope {
   @override
   final List<DartType> typeVariables;
 
   FunctionSignatureBuildingScope(Scope parent, this.typeVariables)
       : super(parent);
 
   String toString() => 'FunctionSignatureBuildingScope($typeVariables)';
 }