Here's a crazy idea. Closures are like objects with private fields, right? Specifically, outside of the function body, you're not allowed to refer to the variables in the closed environment. But one of the most annoying things that happen when I'm debugging is that I want to call some local function, but it's not available from the REPL:
(define (foo x y)
(define (helper z)
... x ... y ...)
...)
What if, at the REPL (i.e., in debug mode only), closures were openable? You could use dot-notation to refer to them, and all you'd have to do is somehow provide the extra bindings needed to fill in their environment. Keyword arguments, maybe?
> ((close foo.helper [#:x 42] [#:y 'blah]) "value of z")
'result-value-ftw!
