Hi,
I noticed that in Racket-6.2.0.2 the function dup-output-port has the wrong type.
The error is in file share\pkgs\typed-racket-lib\typed-racket\base-env\base-env.rkt, where we can find:
[dup-input-port (-Input-Port (B) . ->opt . -Input-Port)]
[dup-output-port (-Output-Port (B) . ->opt . -Input-Port)]
I presume the second line should be:
[dup-output-port (-Output-Port (B) . ->opt . -Output-Port)]
Best,
António.