[racket] weird typed racket error

From: Alexander D. Knauth (alexander at knauth.org)
Date: Sun Jul 13 19:57:48 EDT 2014

For some reason this:
(for/last : (U Index #f)
    ([i : Index (ann (in-range 5) (Sequenceof Index))])
    i)
Is giving me this error:
. Type Checker: type mismatch
  expected: False
  given: Index in: (for/last : (U Index #f) ((i : Index (ann (in-range 5) (Sequenceof Index)))) i)

Why is it expecting False?
And is there some type annotation I can put somewhere to fix it or anything?



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