OutputHandler's constructor is being called. So it would make sense that an explicit call to the constructor should also work.

<snip>
callable Function()

def click():
print("click")

c = Function(null, _addressof_(click))
c()
</snip>

Notice that explicit delegate constructor calls like the one above are not type checked (meaning that the compiler will not complain if the method reference is not compatible with the delegate type).

But does this solve the issue?

def clicked(sender, args as System.EventArgs):
print("clicked!")

clickedHandler = System.EventHandler(null, _addressof_(clicked))
c = Clickable()

c.Click += clicked # this works
c.Click += clickedHandler # this gives compile error

an explicitly created delegate handle fails on assignment with:
BCE0032: The event 'BooCompiler.Tests.Clickable.Click' expects a callable reference compatible with 'System.EventHandler'.

looking at the IL for the working assignment:
L_0008: ldftn void My-delegatesModule::clicked(object, [mscorlib]System.EventArgs)
L_000e: newobj instance void [mscorlib]System.EventHandler::.ctor(object, native int)
L_0013: call instance void [SupportingClasses]BooCompiler.Tests.Clickable::add_Click([mscorlib]System.EventHandler)

It is contructing an EventHandler object but doing the same in boo code give a failure.

def Method(sender as object, e as EventArgs):
print "!!"

h = EventHandler(Method)

BCE0024: The type 'System.EventHandler' does not have a visible constructor that matches the argument list '(callable(System.Object, System.EventArgs) as System.Void)'.

This problem currently requires an ugly hack in the C# parser (involving .EndsWith("EventHandler")...)