Counterintuitive behaviour of bind

To me, bind means 'override everything in this scope'. I'd expect this example to print 2.

@configurable
def func(param=1):
    return param

with func.bind(param=2):
    with func.bind(param=3):
        print(func())

Today's behaviour is that the most deeply nested bind wins, so this actually prints 3. This is at odds with how bind overrides parameters used at the call site (which it does correctly IMO):

@configurable
def func(param=1):
    return param

with func.bind(param=2):
    print(func(param=3))

This does print 2; we test that bind works like this.

TL;DR: bind currently overrides bind calls that are higher in the call stack; we should change it so that higher bind calls win, addressing this TODO.