[racket-dev] seeing compile-time error for Whalesong on HEAD

I'm seeing the following error message on HEAD
(08dc0e10d934cb29b9830a94945c2e38c275a9d8):


application: procedure does not expect an argument with given keyword
  procedure: t->c/both
  given keyword: #:kind
  given arguments:
   Boolean
   #:kind 'impersonator
   #:seen (list (cons
#(struct:#<syntax:/Users/dyoo/work/whalesong/whalesong/promise.rkt:13:20
MyPromise> (Boolean (-> g305) (U Sentinel g305))) #<syntax rec5>))
  context...:
   /Users/dyoo/local/racket/collects/racket/private/kw.rkt:1255:14
   /Users/dyoo/local/racket/collects/typed-racket/private/type-contract.rkt:428:16:
for-loop
   parse-loop178
   /Users/dyoo/local/racket/collects/racket/private/map.rkt:21:13: map
   parse-loop1254
   /Users/dyoo/local/racket/collects/typed-racket/private/type-contract.rkt:215:13
   /Users/dyoo/local/racket/collects/racket/private/map.rkt:21:13: map
   f902
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/provide-handling.rkt:54:2:
mk16
   /Users/dyoo/local/racket/collects/unstable/list.rkt:139:0: map/values
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/provide-handling.rkt:55:4:
mk-untyped-syntax
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/provide-handling.rkt:54:2:
mk16
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/provide-handling.rkt:143:2:
for-loop
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/provide-handling.rkt:49:0:
generate-prov
   /Users/dyoo/local/racket/collects/typed-racket/typecheck/tc-toplevel.rkt:292:0:
type-check
   success...