plt/racket — pull request #621 by takikawa (2014-04-16 20:47:42+00:00)
Title: Remove code that handles #<undefined> in TR

This PR removes the code in `tc-let-unit.rkt` that handles `Undefined` tracking in `letrec` forms. Since Racket no longer allows the values to leak, TR does not necessarily need to track it statically.

This does mean that uninitialized variable errors may occur in code that typechecks, but that is probably more acceptable than false negatives.