[racket] #<undefined> and backward compatibility

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Fri Apr 18 11:00:03 EDT 2014

On Apr 18, 2014, at 10:48 AM, Neil Toronto <neil.toronto at gmail.com> wrote:

> Another benefit is that Typed Racket will no longer have to consider non-function letrec bindings as having the type (U Undefined A) where A is the "real" type. (Technically, (U Undefined A) *was* the real type.)

That was my primary motivation for launching this project, motivated by nearly two decades of coping with such unions or a lack of safety. I knew you'd appreciate it -- Matthias

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