When generating the error message, don't overrun args.nodes .

frog/member.dart

Index: frog/member.dart
===================================================================
--- frog/member.dart	(revision 2524)
+++ frog/member.dart	(working copy)
@@ -959,7 +959,7 @@
         if (arg == null || !parameters[i].isOptional) {
           var msg = _argCountMsg(Math.min(i, args.length), i + 1, atLeast:true);
           return _argError(context, node, target, args, msg,
-              args.nodes[i].span);
+              (i >= args.nodes.length) ? null : args.nodes[i].span);

[jimhug, 2011/12/16 17:29:39]

A better fix would be to use node.span instead of null so that some source
location information is provided.  You can make that change here or in _argError
- using node.span as a fallback when the directly passed span is null.

[dgrove, 2011/12/16 17:49:56]

Done.

         } else {
           argsCode.add(isConst && arg.isConst
               ? arg.canonicalCode : arg.code);