\[\left(\left(\left(x + x\right) + x\right) + x\right) + x\]
\left(\left(\left(x + x\right) + x\right) + x\right) + x
double f(double x) {
        double r8215 = x;
        double r8216 = r8215 + r8215;
        double r8217 = r8216 + r8215;
        double r8218 = r8217 + r8215;
        double r8219 = r8218 + r8215;
        return r8219;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 
(FPCore (x)
  :name "Main:i from "
  (+ (+ (+ (+ x x) x) x) x))

Backtrace

result arity mismatch; expected number of values not received expected: 2 received: 1 in: local-binding form values...: 0LC
loop/data/pavpan/nightlies/herbie/various-cleanup/src/core/extraction.rkt252
(unnamed)/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt260
simplify!/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt2170
run-improve43/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt3390
(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