Error in 0.0ms

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019067 
(FPCore (a b c)
  :name "Area of a triangle"
  :pre (and (<.p16 (real->posit16 0) a) (<.p16 (real->posit16 0) b) (<.p16 (real->posit16 0) c))
  (sqrt.p16 (*.p16 (*.p16 (*.p16 (/.p16 (+.p16 (+.p16 a b) c) (real->posit16 2)) (-.p16 (/.p16 (+.p16 (+.p16 a b) c) (real->posit16 2)) a)) (-.p16 (/.p16 (+.p16 (+.p16 a b) c) (real->posit16 2)) b)) (-.p16 (/.p16 (+.p16 (+.p16 a b) c) (real->posit16 2)) c))))

Backtrace

build-list: contract violation expected: exact-nonnegative-integer? given: '(0)LC
build-list/opt/racket-7.0/collects/racket/private/list.rkt2962
debug-print/data/pavpan/nightlies/herbie/develop/src/debug.rkt1070
run-improve43/data/pavpan/nightlies/herbie/develop/src/mainloop.rkt3460
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128