recode() is very slow due to signal_stage()

[mgirlich]

Most of the time is spend in signal_stage(). This makes recode() so slow that it can't really be used in some situations anymore.

char_vec <- sample(c("a", "b", "c"), 10, replace = TRUE)
bench::mark(
  recode = dplyr::recode(char_vec, a = "Apple", b = "Banana")
)
#> # A tibble: 1 × 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 recode        1.9ms   2.62ms      335.    3.54MB     10.7

^{Created on 2023-07-12 with reprex v2.0.2}

I also opened an issue in lifecycle: r-lib/lifecycle#167

[DavisVaughan]

We will track in r-lib/lifecycle#167