Emit compile-time error on 'const' formal parameters.

sdk/lib/_internal/compiler/implementation/resolution/members.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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Set<Node> get superUses;
 
@@ skipping 3977 matching lines @@
       return null;
     }
     if (!definitions.tail.isEmpty) {
       cancel(definitions.tail.head, 'internal error: extra definition');
       return null;
     }
     Node definition = definitions.head;
     if (definition is NodeList) {
       cancel(node, 'optional parameters are not implemented');
     }
+    if (node.modifiers.isConst()) {
+      error(node, MessageKind.FORMAL_DECLARED_CONST);
+    }
 
     if (currentDefinitions != null) {
       cancel(node, 'function type parameters not supported');
     }
     currentDefinitions = node;
     Element element = definition.accept(this);
     currentDefinitions = null;
     return element;
   }
 
@@ skipping 331 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }