library(tidyr)

tibble(x = 1, data = list(1, 2:3), data2 = list("a", 2:3)) %>% 
  unnest(c(data, data2), ptype = list(data = integer(), data2 = character()))
#> Error in `list_unchop()`:
#> ! Can't convert `x[[2]]` <integer> to <character>.

#> Backtrace:
#>      ▆
#>   1. ├─... %>% ...
#>   2. ├─tidyr::unnest(...)
#>   3. ├─tidyr:::unnest.data.frame(...)
#>   4. │ └─tidyr::unchop(...)
#>   5. │   └─tidyr:::df_unchop(...)
#>   6. │     └─vctrs::list_unchop(col, ptype = col_ptype)
#>   7. └─vctrs (local) `<fn>`()
#>   8.   └─vctrs::vec_default_cast(...)
#>   9.     ├─base::withRestarts(...)
#>  10.     │ └─base (local) withOneRestart(expr, restarts[[1L]])
#>  11.     │   └─base (local) doWithOneRestart(return(expr), restart)
#>  12.     └─vctrs::stop_incompatible_cast(...)
#>  13.       └─vctrs::stop_incompatible_type(...)
#>  14.         └─vctrs:::stop_incompatible(...)
#>  15.           └─vctrs:::stop_vctrs(...)
#>  16.             └─rlang::abort(message, class = c(class, "vctrs_error"), ..., call = vctrs_error_call(call))