Make Invocation.positionalArguments and .namedArguments never be null.

runtime/lib/invocation_mirror_patch.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 _InvocationMirror implements Invocation {
   // Constants describing the invocation type.
   // _FIELD cannot be generated by regular invocation mirrors.
   static const int _METHOD = 0;
   static const int _GETTER = 1;
   static const int _SETTER = 2;
@@ skipping 42 matching lines @@
   Symbol get memberName {
     if (_memberName == null) {
       _setMemberNameAndType();
     }
     return _memberName;
   }
 
   List get positionalArguments {
     if (_positionalArguments == null) {
       int numPositionalArguments = _argumentsDescriptor[1];
+      // Don't count receiver.
+      if (numPositionalArguments == 1) {
+        return _positionalArguments = const [];
+      }
       // Exclude receiver.
       _positionalArguments = _arguments.sublist(1, numPositionalArguments);
     }
     return _positionalArguments;
   }
 
   Map<Symbol, dynamic> get namedArguments {
     if (_namedArguments == null) {
-      _namedArguments = new Map<Symbol, dynamic>();
       int numArguments = _argumentsDescriptor[0] - 1;  // Exclude receiver.
       int numPositionalArguments = _argumentsDescriptor[1] - 1;
       int numNamedArguments = numArguments - numPositionalArguments;
+      if (numNamedArguments == 0) {
+        return _namedArguments = const <Symbol, dynamic>{};
+      }
+      _namedArguments = new Map<Symbol, dynamic>();
       for (int i = 0; i < numNamedArguments; i++) {
         String arg_name = _argumentsDescriptor[2 + 2*i];
         var arg_value = _arguments[_argumentsDescriptor[3 + 2*i]];
         _namedArguments[new _collection_dev.Symbol.unvalidated(arg_name)] =
             arg_value;
       }
     }
     return _namedArguments;
   }
 
@@ skipping 42 matching lines @@
       native "InvocationMirror_invoke";
 
   _invokeOn(Object receiver) {
     return _invoke(receiver, _functionName, _argumentsDescriptor, _arguments);
   }
 
   // TODO(ahe): This is a hack.  See _LocalInstanceMirrorImpl.delegate
   // in mirrors_impl.dart
   static final _invokeOnClosure = (x, y) => y._invokeOn(x);
 }