Cannot store function with lifetime dependence in variable

Sorry, we don't have the type system support yet for using a closure capture as the source of a lifetime dependency. Not because it's difficult; just lack of time.

On main, you'll get the message:

error: lifetime-dependent value escapes its scope
note: it depends on a closure capture; this is not yet supported

I'm not sure how to work around it short of capturing state in a struct and passing that rather than a function type.