I can confirm that the same issue exists with JRuby 1.1.1

Script that works in MRI, fails in JRuby 1.1.1, thus reproducing the issue

Confirmed...really weird.

In CallSite.java:102 the call to method.isCallableFrom fails because the current frame has erroneously had its self object set to the string passed into the method (="current"). It would seem highly likely that the code below is the culprit, as it is evaluated prior to isCallableFrom failing:

CallBlock.java:82

public IRubyObject yield(ThreadContext context, IRubyObject value, IRubyObject self,
RubyModule klass, boolean aValue, Binding binding, Block.Type type) {
if (klass == null) { self = binding.getSelf(); // FIXME: We never set this back! binding.getFrame().setSelf(self); }

return callback.call(context, new IRubyObject[] {value}, Block.NULL_BLOCK);
}

Sorry, that's (from CallBlock.java:82 in trunk):

public IRubyObject yield(ThreadContext context, IRubyObject value, IRubyObject self, 
            RubyModule klass, boolean aValue, Binding binding, Block.Type type) {
        if (klass == null) {
            self = binding.getSelf();
            // FIXME: We never set this back!
            binding.getFrame().setSelf(self);
        }
        
        return callback.call(context, new IRubyObject[] {value}, Block.NULL_BLOCK);
    }

Attaching a patch which seems to fix the issue, while keeping the tests running.

Testcase for inclusion in the unit test suite.

I committed a slightly modified version of this patch that uses try/finally to guarantee the frame self gets set back. Thanks Steen!

Thanks Charlie! You could even take out the line "// FIXME: We never set this back!" since now we do