Codegen support for the argument definition test.

lib/compiler/implementation/compile_time_constants.dart

 // Copyright (c) 2012, 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.
 
 class Constant implements Hashable {
   const Constant();
 
   bool isNull() => false;
   bool isBool() => false;
   bool isTrue() => false;
   bool isFalse() => false;
   bool isInt() => false;
   bool isDouble() => false;
   bool isNum() => false;
   bool isString() => false;
   bool isList() => false;
   bool isMap() => false;
   bool isConstructedObject() => false;
   bool isFunction() => false;
   /** Returns true if the constant is null, a bool, a number or a string. */
   bool isPrimitive() => false;
   /** Returns true if the constant is a list, a map or a constructed object. */
   bool isObject() => false;
+  bool isSentinel() => false;
 
   bool isNaN() => false;
 
   abstract void _writeJsCode(CodeBuffer buffer, ConstantHandler handler);
   /**
     * Unless the constant can be emitted multiple times (as for numbers and
     * strings) adds its canonical name to the buffer.
     */
   abstract void _writeCanonicalizedJsCode(CodeBuffer buffer,
                                           ConstantHandler handler);
   abstract List<Constant> getDependencies();
 }
 
+class SentinelConstant extends Constant {
+  const SentinelConstant();
+  static final SENTINEL = const SentinelConstant();
+
+  void _writeJsCode(CodeBuffer buffer, ConstantHandler handler) {
+    handler.compiler.internalError(
+        "The parameter sentinel constant does not need specific JS code");
+  }
+
+  void _writeCanonicalizedJsCode(CodeBuffer buffer, ConstantHandler handler) {
+    buffer.add(handler.compiler.namer.CURRENT_ISOLATE);
+  }
+
+  List<Constant> getDependencies() => const <Constant>[];
+
+  // Just use a randome value.
+  int hashCode() => 9264297841582447;
+
+  bool isSentinel() => true;
+}
+
 class FunctionConstant extends Constant {
   Element element;
 
   FunctionConstant(this.element);
 
   bool isFunction() => true;
 
   bool operator ==(var other) {
     if (other is !FunctionConstant) return false;
     return other.element === element;
@@ skipping 1163 matching lines @@
       Constant fieldValue = fieldValues[field];
       if (fieldValue === null) {
         // Use the default value.
         fieldValue = compiler.compileVariable(field);
       }
       jsNewArguments.add(fieldValue);
     });
     return jsNewArguments;
   }
 }