Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2020231 
(FPCore (x.re x.im y.re y.im)
  :name "_divideComplex, imaginary part"
  :precision binary64
  (/ (- (* x.im y.re) (* x.re y.im)) (+ (* y.re y.re) (* y.im y.im))))

Backtrace

hash-ref: no value found for key key: 'x.im		L	C
table-ref	/data/pavpan/nightlies/herbie/cleanup/src/common.rkt	32	0
f284	unknown
munge	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	138	2
for-loop	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	159	15
f284	unknown
munge	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	138	2
for-loop	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	159	15
f284	unknown
munge	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	138	2
for-loop	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	159	15
f284	unknown
munge	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	138	2
for-loop	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	170	4
batch-eval-progs	/data/pavpan/nightlies/herbie/cleanup/src/programs.rkt	112	0
batch-errors	/data/pavpan/nightlies/herbie/cleanup/src/points.rkt	169	0
atab-add-altns	/data/pavpan/nightlies/herbie/cleanup/src/core/alt-table.rkt	194	0
(unnamed)	/opt/racket-7.5/collects/racket/contract/private/arrow-val-first.rkt	486	18
finalize-iter!	/data/pavpan/nightlies/herbie/cleanup/src/mainloop.rkt	278	0
run-improve41	/data/pavpan/nightlies/herbie/cleanup/src/mainloop.rkt	365	0
.../more-scheme.rkt:261:28	unknown
run	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.5/collects/racket/private/more-scheme.rkt	261	28

Reproduce

herbie shell --seed 2020231 
(FPCore (x.re x.im y.re y.im)
  :name "_divideComplex, imaginary part"
  :precision binary64
  (/ (- (* x.im y.re) (* x.re y.im)) (+ (* y.re y.re) (* y.im y.im))))